Understanding your vehicle’s health is now more accessible than ever, thanks to EOBD OBDII live data. This manual serves as your comprehensive guide to deciphering the wealth of information available through your vehicle’s On-Board Diagnostics (OBDII) system. Whether you are a seasoned mechanic or a car enthusiast, mastering live data is crucial for accurate and efficient vehicle diagnostics.
OBDII, the standardized system mandated for most vehicles since the mid-1990s, provides real-time insights into your car’s engine and related systems. Live data, also known as Parameter Identifiers (PIDs), is the stream of information transmitted by your vehicle’s sensors and control modules. This data encompasses a wide range of parameters, from engine RPM and speed to fuel trim and emissions control statuses. By accessing and interpreting this data, you can pinpoint issues, monitor performance, and ensure your vehicle runs optimally.
This manual breaks down the essential OBDII live data parameters, offering clear descriptions and explanations of their significance in vehicle operation and diagnostics.
Vehicle Operation Parameters: Monitoring Engine and Performance
This section details the live data parameters related to the fundamental operation of your vehicle’s engine and overall performance. Understanding these parameters is the first step in diagnosing a wide array of potential issues.
Engine RPM (Revolutions Per Minute)
Description: Engine RPM measures how many times the engine crankshaft completes a full rotation in one minute. It’s a fundamental indicator of engine speed and activity.
Diagnostic Significance:
- Idle RPM: A normal idle RPM ensures the engine runs smoothly when stationary. High or low idle RPM can indicate vacuum leaks, throttle body issues, or problems with the idle air control system.
- RPM Fluctuation: Erratic RPM readings can point to misfires, sensor malfunctions, or fuel delivery problems.
- Performance Monitoring: RPM is crucial for assessing engine performance under load and during acceleration.
Vehicle Speed
Description: This parameter reports the current speed of your vehicle, typically derived from wheel speed sensors.
Diagnostic Significance:
- Speedometer Verification: Compare live data speed with your speedometer reading to check for discrepancies, which may indicate issues with speed sensors or instrument cluster.
- ABS/Traction Control Diagnostics: Speed data is essential for diagnosing problems within the Anti-lock Braking System (ABS) and Traction Control System (TCS).
- Transmission Issues: Incorrect speed readings can contribute to transmission shifting problems.
Engine Coolant Temperature
Description: Measured by a sensor in the engine coolant, this parameter indicates the temperature of the engine’s coolant.
Diagnostic Significance:
- Overheating: High coolant temperatures are a critical warning sign of potential overheating, which can lead to severe engine damage. Check for coolant leaks, thermostat malfunctions, or radiator fan issues.
- Thermostat Function: Monitoring coolant temperature during warm-up can help diagnose thermostat problems (e.g., stuck open or closed).
- Sensor Accuracy: Compare live data with the temperature gauge on your dashboard to verify sensor accuracy.
Engine Oil Temperature
Description: This parameter reflects the temperature of the engine oil, measured by a dedicated sensor.
Diagnostic Significance:
- Lubrication Efficiency: Oil temperature affects its viscosity and lubricating properties. Overly high temperatures can degrade oil and increase engine wear.
- Performance Driving: Monitoring oil temperature is particularly important in performance driving or heavy-duty applications to prevent oil breakdown.
- Cooling System Issues: Elevated oil temperatures can sometimes indicate problems with the engine cooling system.
Ambient Air Temperature
Description: The temperature of the air outside the vehicle, measured by a sensor typically located in the front bumper area.
Diagnostic Significance:
- Engine Performance Calculations: The Engine Control Unit (ECU) uses ambient air temperature data to adjust fuel and ignition timing for optimal engine performance in varying conditions.
- Air Conditioning System: Ambient temperature is a factor in the operation of the vehicle’s air conditioning system.
- Sensor Accuracy: Compare readings with external thermometers to verify sensor accuracy.
Barometric Pressure
Description: Also known as atmospheric pressure, barometric pressure is measured by a BARO sensor.
Diagnostic Significance:
- Altitude Compensation: The ECU uses barometric pressure readings to compensate for altitude changes, which affect air density and thus engine performance.
- Fuel Trim and Timing Adjustments: Accurate barometric pressure data is crucial for the ECU to correctly adjust fuel trim and engine timing for optimal combustion.
- Sensor Malfunction: Incorrect readings can lead to improper fuel mixture and performance issues.
Accelerator Pedal Position & Relative Accelerator Pedal Position
Description: These parameters indicate the position of the accelerator pedal. “Accelerator Pedal Position” is the raw reading, while “Relative Accelerator Pedal Position” may be adjusted or averaged based on multiple sensors.
Diagnostic Significance:
- Throttle Response Issues: Inconsistencies between pedal position and engine response can indicate problems with the accelerator pedal sensor, throttle actuator, or related wiring.
- Cruise Control Diagnostics: Accelerator pedal position is a key input for the cruise control system.
- Sensor Calibration: Monitoring these parameters can help identify sensor calibration issues. Note that “Relative Accelerator Pedal Position” might not always read 100% when the pedal is fully depressed due to sensor variations and vehicle-specific programming.
Commanded Throttle Actuator & Relative Throttle Position & Absolute Throttle Position
Description:
- Commanded Throttle Actuator: The throttle position requested by the ECU based on driver input (accelerator pedal) and other factors.
- Relative Throttle Position: Compares the current throttle position to a learned closed position, compensating for carbon buildup or other factors affecting throttle behavior.
- Absolute Throttle Position: The actual opening of the throttle valve, from 0% (closed) to 100% (fully open).
Diagnostic Significance:
- Throttle Body Problems: Discrepancies between commanded and actual throttle position can pinpoint issues with the throttle body, throttle position sensor (TPS), or throttle actuator motor.
- Idle Control: Throttle position is critical for idle control. Issues here can lead to stalling or rough idling.
- Performance and Response: Monitoring throttle position during acceleration can reveal problems affecting engine responsiveness. Carbon buildup can affect “Relative Throttle Position” readings over time.
Control Module Voltage
Description: This parameter shows the voltage supplied to the Engine Control Unit (ECU).
Diagnostic Significance:
- Power Supply Issues: Low or unstable control module voltage can indicate problems with the vehicle’s charging system (alternator, battery), wiring, or grounds.
- ECU Malfunction: Insufficient voltage can lead to erratic ECU behavior and various diagnostic trouble codes.
- System Stability: Monitoring voltage helps ensure the ECU and its sensors receive stable power for accurate readings and proper operation. Note: This is not the same as battery voltage.
Hybrid Battery Pack Remaining Life & Hybrid/EV Vehicle System Status
Description: These parameters are specific to hybrid and electric vehicles (EVs).
- Hybrid Battery Pack Remaining Life: The percentage of charge remaining in the hybrid battery pack. Standard OBDII typically does not provide individual cell data.
- Hybrid/EV Vehicle System Status: Provides details on the status of hybrid/EV systems, including:
- HEV Charging State: Charge Sustaining Mode (CSM) or Charge Depletion Mode (CDM). Non-PHEVs usually operate in permanent CSM.
- HEV Battery Voltage: Voltage of the hybrid battery pack (0V to 1024V range).
- HEV Battery Current: Current flow in/out of the hybrid battery (- value indicates charging, range -3300A to 3300A).
Diagnostic Significance:
- Hybrid Battery Health: “Hybrid Battery Pack Remaining Life” gives a general indication of battery charge level. More detailed diagnostics require specialized hybrid/EV scan tools.
- Charging System Issues: “HEV Charging State,” “HEV Battery Voltage,” and “HEV Battery Current” are crucial for diagnosing problems within the hybrid/EV charging system and battery management system.
- System Operation Mode: Understanding CSM and CDM modes helps interpret hybrid system behavior.
Calculated Engine Load Value & Absolute Load Value
Description:
- Calculated Engine Load Value: An estimated percentage of engine load, based on Mass Air Flow (MAF) sensor readings relative to peak airflow. Altitude correction is applied.
- Absolute Load Value: A normalized percentage value of air mass per intake stroke, calculated by dividing the actual air mass by the air mass at 100% throttle.
Diagnostic Significance:
- Engine Efficiency and Performance: Load values reflect how hard the engine is working. High load can indicate issues causing engine strain.
- MAF Sensor Diagnosis: “Calculated Engine Load Value” relies on MAF sensor data, so abnormal readings can point to MAF sensor problems or intake leaks.
- Idle vs. Load Conditions: “Absolute Load Value” varies with vehicle state (idle, parking, accessories on/off), reflecting changes in engine load.
Driver’s Demand Engine – Percent Torque & Actual Engine – Percent Torque & Engine Friction – Percent Torque & Engine Reference Torque & Engine Percent Torque Data
Description: These parameters relate to engine torque, a measure of rotational force.
- Driver’s Demand Engine – Percent Torque: The maximum available engine torque percentage based on driver input (accelerator), cruise control, and transmission requests. External factors like traction control do not affect this value.
- Actual Engine – Percent Torque: Also known as Indicated Torque, the current percentage of total available engine torque, net brake torque, and friction torque.
- Engine Friction – Percent Torque: The percentage of torque required to overcome engine friction (internal components, fuel pump, water pump, etc.) when running without load.
- Engine Reference Torque: A fixed torque rating considered 100% for “Actual Engine Percent Torque” and other percentage-based torque parameters. This value is constant.
- Engine Percent Torque Data: A parameter used when vehicle condition changes can cause torque reference to change.
Diagnostic Significance:
- Torque Delivery Issues: Comparing “Driver’s Demand” and “Actual Engine Torque” can reveal problems with engine performance, fuel delivery, or ignition.
- Engine Efficiency: “Engine Friction Torque” provides insights into engine mechanical efficiency. High friction can indicate wear or lubrication issues.
- Performance Tuning: These parameters are important for performance tuning and engine performance analysis.
Auxiliary Input/Output
Description: A composite data point providing status details for various vehicle systems:
- Power Take Off (PTO) and Glow Plug Lamp (On/Off)
- Automatic Transmission Park/Neutral or Drive/Reverse Status
- Manual Transmission Neutral/Clutch In or In Gear Status
- Recommended Transmission Gear (1 to 15 Status)
Diagnostic Significance:
- System Status Monitoring: Consolidates status information from multiple auxiliary systems for quick overview.
- Transmission Diagnostics: Provides data relevant to automatic and manual transmission operation.
- PTO System Monitoring: Useful for vehicles equipped with Power Take Off systems (e.g., work trucks).
Exhaust Gas Temperature (EGT)
Description: Measured by sensors in the exhaust system, EGT monitors temperatures in critical components:
- Turbocharger
- Catalytic Converter
- Diesel Particulate Filter (DPF)
- NOx Reduction System Components
Diagnostic Significance:
- Overheating Prevention: EGT sensors protect components from critical overheating, which can cause damage.
- Catalytic Converter Efficiency: Monitoring catalytic converter EGT is important for assessing its efficiency and preventing damage.
- DPF Regeneration Monitoring: EGT data is crucial for monitoring Diesel Particulate Filter regeneration processes.
- Turbocharger Health: High EGTs can indicate turbocharger stress or malfunction.
Engine Exhaust Flow Rate
Description: The flow rate of the air-fuel mixture after combustion. Calculated using exhaust temperature, volumetric efficiency, engine size, and RPM.
Diagnostic Significance:
- Engine Performance Analysis: Exhaust flow rate is an indicator of overall engine performance and efficiency.
- Exhaust System Restrictions: Abnormal flow rates can suggest restrictions in the exhaust system.
- Combustion Efficiency: Flow rate can indirectly reflect combustion efficiency.
Exhaust Pressure
Description: Pressure within the exhaust system, typically reported as absolute pressure. Reads close to ambient atmospheric pressure when the engine is off.
Diagnostic Significance:
- Exhaust System Blockages: High exhaust pressure readings can indicate blockages in the exhaust system (e.g., clogged catalytic converter or muffler).
- Engine Backpressure Issues: Excessive backpressure can reduce engine performance and efficiency.
- Sensor Location: Data may be reported from one or two exhaust locations depending on vehicle configuration.
Manifold Surface Temperature
Description: The temperature of the exhaust manifold’s outer surface.
Diagnostic Significance:
- Exhaust System Heat Monitoring: Provides another point of temperature monitoring in the exhaust system.
- Overheat Detection: High manifold surface temperatures can indicate localized overheating issues.
- Component Protection: Helps assess heat management in the engine bay.
Timing Advance for #1 Cylinder
Description: The timing advance is the angle relative to Top Dead Center (TDC) when the #1 cylinder spark plug fires.
Diagnostic Significance:
- Ignition Timing Issues: Incorrect timing advance can lead to poor engine performance, misfires, and increased emissions.
- Engine Knock/Detonation: Excessive timing advance can cause engine knock or detonation, which is damaging to the engine.
- Manufacturer Specifications: Timing advance is manufacturer-specific. Positive values mean delayed spark, negative means spark before TDC.
Engine Run Time & Run Time Since Engine Start & Time Run with MIL On & Distance Traveled while MIL is Activated & Time since Trouble Codes Cleared & Distance Traveled Since Codes Cleared & Warm-ups Since Codes Cleared
Description: These parameters track various engine run time and driving statistics.
- Engine Run Time: Total engine run time (seconds), idle time (seconds), and PTO engaged time.
- Run Time Since Engine Start: Run time since the last engine start (seconds).
- Time Run with MIL On: Engine run time since the Malfunction Indicator Lamp (MIL, check engine light) turned on. Starts counting when a code is thrown.
- Distance Traveled while MIL is Activated: Distance traveled since the MIL activated. Resets when codes are cleared or battery disconnected.
- Time since Trouble Codes Cleared: Engine run time since codes were cleared (by scan tool or battery disconnect).
- Distance Traveled Since Codes Cleared: Distance traveled since codes were cleared. Does not reset if non-engine codes are cleared.
- Warm-ups Since Codes Cleared: Number of engine warm-up cycles since code clearing or battery disconnect. A warm-up cycle is defined by coolant temperature reaching 40°F after startup and then reaching at least 170°F.
Diagnostic Significance:
- Fault History Tracking: “Time Run with MIL On” and “Distance Traveled while MIL is Activated” help assess how long a fault has been present and its impact.
- Post-Repair Verification: “Time since Trouble Codes Cleared” and “Distance Traveled Since Codes Cleared” are useful for verifying repairs and ensuring faults do not return after clearing codes.
- Warm-up Cycle Monitoring: “Warm-ups Since Codes Cleared” can be relevant for emissions testing readiness and diagnostic procedures.
Fuel & Air Parameters: Monitoring Mixture and Delivery
These parameters provide critical insights into the fuel and air systems, essential for efficient combustion and emissions control.
Fuel System Status
Description: Indicates the operating mode of the fuel system:
- Open Loop Mode: ECU uses pre-programmed air-fuel ratios, ignoring oxygen sensor feedback.
- Closed Loop Mode: ECU uses oxygen sensor feedback to adjust air-fuel ratio for optimal combustion.
Diagnostic Significance:
- Fuel Control System Operation: Helps determine if the fuel system is operating in open or closed loop. Open loop operation for extended periods can indicate sensor or system issues.
- Oxygen Sensor Dependency: Closed loop operation relies on functional oxygen sensors.
Oxygen Sensor Voltage & Oxygen Sensor Equivalence Ratio & Oxygen Sensor Current
Description: These parameters relate to oxygen sensor readings, crucial for air-fuel mixture control.
- Oxygen Sensor Voltage: Voltage generated by the oxygen sensor (typical range 0.1V – 0.9V). Indicates oxygen content in the exhaust.
- Oxygen Sensor Equivalence Ratio (Lambda): Indicates air-fuel mixture richness or leanness. Used by the ECU in closed loop mode. Ignored in open loop.
- Oxygen Sensor Current: Current flow within the oxygen sensor. 0mA indicates balanced mixture. Positive current is lean (excess air), negative is rich (excess fuel).
Diagnostic Significance:
- Air-Fuel Ratio Monitoring: Oxygen sensor data is fundamental for monitoring and controlling the air-fuel mixture.
- Sensor Functionality: Voltage readings outside the normal range (0.1V-0.9V) can indicate a faulty oxygen sensor.
- Lean/Rich Conditions: Current and equivalence ratio readings help diagnose lean or rich fuel mixture conditions.
Short Term Fuel Trim & Long Term Fuel Trim
Description: Fuel trim values represent adjustments made by the ECU to the base fuel mixture.
- Short Term Fuel Trim (STFT): Immediate, dynamic adjustments made in response to oxygen sensor feedback.
- Long Term Fuel Trim (LTFT): Learned adjustments accumulated over time to compensate for longer-term changes (e.g., injector wear, intake leaks). LTFT updates take seconds and are stored in ECU memory.
Diagnostic Significance:
- Fuel Mixture Adaptations: Fuel trim values indicate how much the ECU is compensating for deviations from the ideal air-fuel ratio.
- Lean/Rich Condition Diagnosis:
- Positive Fuel Trim (STFT & LTFT): ECU is adding fuel, indicating a lean condition (too much air).
- Negative Fuel Trim (STFT & LTFT): ECU is removing fuel, indicating a rich condition (too much fuel).
- Underlying Issues: High fuel trim values (positive or negative) suggest underlying problems like vacuum leaks, fuel pressure issues, or sensor malfunctions that are causing the ECU to compensate excessively.
Commanded Equivalence Ratio (CER)
Description: The air-fuel ratio requested by the ECU, also known as Lambda.
Diagnostic Significance:
- Air-Fuel Ratio Targets: CER reflects the ECU’s target air-fuel ratio.
- Open vs. Closed Loop Behavior:
- Wide Range O2 Sensors: CER displayed in both open and closed loop.
- Conventional O2 Sensors: CER displayed in open loop, typically 1.0 in closed loop.
- Mixture Control Monitoring: Helps understand the ECU’s fuel mixture control strategy.
Mass Air Flow Rate (MAF)
Description: Measures the mass of air entering the engine per unit of time.
Diagnostic Significance:
- Air Intake Measurement: MAF sensor is crucial for accurate air intake measurement, essential for fuel mixture calculations.
- MAF Sensor Problems: Low or erratic MAF readings can indicate a faulty MAF sensor, intake leaks after the MAF sensor, or air filter restrictions.
- Performance Range: Typical idle range: 2-7 g/s, 2500 RPM range: 15-25 g/s. Refer to manufacturer specs for precise values.
Intake Air Temperature (IAT)
Description: The temperature of the air entering the engine cylinders. Vehicles may have multiple IAT sensors for different purposes (engine intake air, climate control, ambient air).
Diagnostic Significance:
- Air Density Compensation: IAT data is used by the ECU to adjust fuel and timing based on air density changes with temperature.
- Sensor Functionality: Incorrect IAT readings can lead to improper air-fuel mixture and performance issues.
- Multiple Sensor Applications: Be aware of different IAT sensor locations and their specific functions in the vehicle.
Intake Manifold Absolute Pressure (MAP)
Description: The absolute pressure inside the intake manifold, measured by a MAP sensor.
Diagnostic Significance:
- Manifold Vacuum Monitoring: MAP sensor measures intake manifold vacuum, which is related to engine load.
- Vacuum Leak Detection: Abnormally low vacuum (high MAP reading) at idle can indicate vacuum leaks.
- Engine Load and Airflow Calculation: MAP data is used by the ECU to estimate engine load and airflow.
- Typical Values: Running engine: 18-20 “Hg vacuum, Idle engine: 0-20 “Hg vacuum.
Fuel Pressure (Gauge) & Fuel Rail Pressure & Fuel Rail Pressure (Absolute) & Fuel Rail Pressure (relative to manifold vacuum)
Description: These parameters report fuel pressure at various points in the fuel system.
- Fuel Pressure (Gauge): Fuel pressure relative to atmospheric pressure (0 indicates atmospheric pressure).
- Fuel Rail Pressure: Gauge pressure in the fuel rail.
- Fuel Rail Pressure (Absolute): Absolute pressure in the fuel rail (includes atmospheric pressure).
- Fuel Rail Pressure (relative to manifold vacuum): Fuel pressure relative to intake manifold vacuum.
Diagnostic Significance:
- Fuel Delivery Problems: Low fuel pressure can indicate fuel pump issues, fuel filter blockages, or fuel pressure regulator malfunctions.
- Fuel Pressure Regulator Diagnosis: Monitoring fuel pressure (especially relative to manifold vacuum) helps diagnose fuel pressure regulator operation.
- Pressure Sensor Issues: Incorrect readings can point to faulty fuel pressure sensors.
Alcohol Fuel %
Description: The percentage of ethanol/alcohol content in the fuel, measured by the engine computer.
Diagnostic Significance:
- Flex Fuel Vehicle Monitoring: Important for flex-fuel vehicles designed to run on varying ethanol blends (e.g., E85).
- Fuel Composition Verification: Verifies fuel composition and ensures it matches vehicle requirements.
- Fuel Sensor Accuracy: Incorrect readings can affect fuel mixture calculations and performance. Example: E85 blend should read around 85%.
Fuel Level Input
Description: The percentage of fuel remaining in the fuel tank, based on fuel level sensor readings.
Diagnostic Significance:
- Fuel Gauge Verification: Compare live data with the fuel gauge to check for discrepancies, which may indicate fuel level sensor or gauge issues.
- Fuel System Monitoring: General fuel level monitoring for diagnostics and fuel management.
Engine Fuel Rate & Cylinder Fuel Rate
Description:
- Engine Fuel Rate: Near-instantaneous fuel consumption rate (Liters or Gallons per hour), calculated by the ECU based on fuel used in the last 1000ms. Does not include fuel for diesel aftertreatment.
- Cylinder Fuel Rate: Calculated fuel injected per cylinder per intake stroke (mg/stroke).
Diagnostic Significance:
- Fuel Consumption Monitoring: “Engine Fuel Rate” provides real-time fuel consumption data.
- Fuel Injector Performance: “Cylinder Fuel Rate” can help identify imbalances in fuel delivery between cylinders.
- Efficiency Analysis: Fuel rate data is useful for fuel efficiency analysis and diagnostics.
Fuel System Percentage Use
Description: Percentage of total fuel usage for each cylinder bank (up to four banks). Can display data for two separate fuel systems (e.g., diesel & CNG) if supported.
Diagnostic Significance:
- Fuel Distribution Balance: Helps assess fuel distribution balance between cylinder banks.
- Dual Fuel System Monitoring: For vehicles with dual fuel systems, monitors usage in each system.
Fuel Injection Timing
Description: The angle of crankshaft rotation before Top Dead Center (BTDC) at which fuel injection begins. Positive angle is before TDC, negative is after TDC.
Diagnostic Significance:
- Injection Timing Accuracy: Correct fuel injection timing is crucial for efficient combustion and emissions control.
- Timing Issues: Incorrect timing can lead to poor performance, increased emissions, and engine damage.
- BTDC/ATDC Indication: Positive/negative angle indicates injection timing relative to TDC.
Fuel System Control
Description: Reports status information for diesel fuel systems (systems 1 & 2 if supported):
- Fuel pressure control (Closed/Open loop)
- Fuel injection quantity (Closed/Open loop)
- Fuel injection timing (Closed/Open loop)
- Idle fuel balance/contribution (Closed/Open loop)
Closed loop means sensor feedback is used for fine-tuning. System 2 may not be used on all vehicles.
Diagnostic Significance:
- Diesel Fuel System Operation: Provides detailed status of diesel fuel system control loops.
- Control Loop Diagnostics: Helps diagnose issues within the fuel pressure, injection quantity, timing, and idle control systems.
Fuel Pressure Control System & Injection Pressure Control System
Description:
- Fuel Pressure Control System: For up to two fuel rails, reports: Commanded rail pressure, Actual rail pressure, Temperature. Pressure is gauge pressure.
- Injection Pressure Control System (Diesels with Oil-Actuated Injection): For diesels using oil pressure for fuel injection, reports: Commanded Control Pressure Rail A/B, Actual Pressure Rail A/B.
Diagnostic Significance:
- Fuel Rail Pressure Monitoring: “Fuel Pressure Control System” monitors fuel rail pressure and temperature.
- Diesel Injection System Diagnostics: “Injection Pressure Control System” is specific to diesels with high-pressure oil injection (HEUI) systems, allowing diagnostics of the oil-side pressure control.
- Pressure Sensor and Pump Issues: Discrepancies between commanded and actual pressures can point to sensor, pump, or regulator problems.
Boost Pressure Control
Description: For turbocharged vehicles, reports: ECM commanded boost pressure, Actual boost pressure (for one or two turbos). All data is absolute pressure.
Diagnostic Significance:
- Turbocharger Boost Monitoring: Essential for diagnosing turbocharger and boost control system issues.
- Boost Leaks and Control Problems: Discrepancies between commanded and actual boost can indicate boost leaks, wastegate problems, or boost control solenoid issues.
- Pressure Units: Reported in absolute pressure. To get gauge pressure (boost level), subtract atmospheric pressure (approx. 14.7 psi). Example: 24.7 psi absolute = 10 psi gauge boost.
- Boost Control Mode Feedback: Provides status on boost control system operating mode (Open Loop, Closed Loop, Fault Present).
Turbocharger RPM & Turbocharger Temperature & Turbocharger Compressor Inlet Pressure Sensor
Description: These parameters provide further details on turbocharger operation.
- Turbocharger RPM: Turbine RPM of one or both turbos (max value 655,350 rpm).
- Turbocharger Temperature: Reports temperatures for one or both turbos: Compressor inlet/outlet temperature (charge air), Turbine inlet/outlet temperature (exhaust gas). Charge air temp range: -40 to 215 °C, Exhaust temp range: -40 to 6513.5 °C.
- Turbocharger Compressor Inlet Pressure Sensor: Pressure at the turbocharger inlet (absolute pressure).
Diagnostic Significance:
- Turbocharger Performance and Health: “Turbocharger RPM” and “Turbocharger Temperature” provide detailed insights into turbocharger operation and potential stress.
- Over-Speeding and Overheating: Monitoring RPM and temperature helps prevent turbocharger damage from over-speeding or overheating.
- Pressure Reference: “Turbocharger Compressor Inlet Pressure Sensor” gives a reference pressure point before the turbocharger.
Variable Geometry Turbo (VGT) Control & Wastegate Control
Description: These parameters relate to turbocharger boost control mechanisms.
- Variable Geometry Turbo (VGT) Control: For VGT turbos, reports: Commanded VGT Position, Actual VGT Vane Position, VGT Control Status (Open/Closed Loop, Fault State). 0% vane position = max bypass, 100% = max boost.
- Wastegate Control: For electronic wastegate systems, reports: Commanded wastegate position, Actual wastegate position (0% closed, 100% max bypass).
Diagnostic Significance:
- Boost Control System Diagnostics: “VGT Control” and “Wastegate Control” are crucial for diagnosing issues with variable geometry turbo and wastegate systems.
- Actuator and Sensor Problems: Discrepancies between commanded and actual positions can indicate actuator malfunctions or sensor problems.
- Boost Response Issues: Incorrect VGT or wastegate operation can lead to poor boost response or overboost conditions.
Charge Air Cooler Temperature (CACT)
Description: Temperature of the intercooler air charge for turbocharged vehicles, with up to four sensors: Bank 1 Sensor 1/2, Bank 2 Sensor 1/2. Sensor mapping may require factory manual.
Diagnostic Significance:
- Intercooler Efficiency: CACT monitoring helps assess intercooler efficiency in cooling the compressed intake air.
- Overheating and Performance Loss: High CACT indicates reduced intercooler efficiency, leading to hotter intake air, reduced engine performance, and potential knock.
- Sensor Location: Refer to factory manual for sensor locations as SAE/OBDII standard does not specify default mapping.
Emissions Control Parameters: Monitoring System Efficiency
This section covers parameters related to the vehicle’s emissions control systems, crucial for environmental compliance and diagnosing emissions-related faults.
Commanded EGR & EGR Error
Description:
- Commanded EGR: The desired opening percentage of the Exhaust Gas Recirculation (EGR) valve (0% closed, 100% open).
- EGR Error: Percentage difference between actual and commanded EGR opening. EGR Error = (Actual – Commanded) / Commanded.
Diagnostic Significance:
- EGR System Operation: “Commanded EGR” shows the ECU’s EGR valve control strategy.
- EGR Valve Problems: Significant “EGR Error” can indicate EGR valve sticking, actuator malfunctions, or sensor issues.
- Error Calculation Note: EGR Error calculation behaves specifically when Commanded EGR is 0%.
Commanded Diesel Intake Air Flow Control
Description: Also known as EGR Throttle. For newer diesels with intake throttle plates for EGR control, reports: Commanded position of intake air flow throttle, Actual position of EGR throttle (primary and secondary if fitted).
Diagnostic Significance:
- EGR Throttle System Operation: Monitors the operation of EGR throttle plates used in some diesel engines to create intake vacuum for EGR flow.
- Throttle Plate Issues: Discrepancies between commanded and actual positions can indicate throttle plate malfunctions.
Exhaust Gas Recirculation Temperature
Description: Reports up to four EGR temperature values: EGRTA (Bank 1 Pre-Cooler), EGRTB (Bank 1 Post-Cooler), EGRTC (Bank 2 Pre-Cooler), EGRTD (Bank 2 Post-Cooler).
Diagnostic Significance:
- EGR Cooler Efficiency: EGR temperature monitoring helps assess the efficiency of EGR coolers in reducing exhaust gas temperature before recirculation.
- EGR System Performance: Temperature values are relevant for overall EGR system performance and diagnostics.
EVAP System Vapor Pressure & Absolute Evap System Vapor Pressure & Commanded Evaporative Purge
Description: Parameters related to the Evaporative Emission Control (EVAP) system.
- EVAP System Vapor Pressure: Gauge pressure in the EVAP system.
- Absolute Evap System Vapor Pressure: Absolute pressure in the EVAP system.
- Commanded Evaporative Purge: EVAP purge flow rate requested by the ECU (0% closed, 100% max purge).
Diagnostic Significance:
- EVAP System Leaks: Pressure readings are crucial for diagnosing EVAP system leaks.
- Purge Valve Operation: “Commanded Evaporative Purge” and pressure readings help assess the operation of the EVAP purge valve and system.
- Sensor Location: Sensor locations may vary (fuel tank or EVAP line). Refer to factory manual.
Catalyst Temperature
Description: Temperature of the catalytic converter. “Bank #” indicates engine side, “Sensor #” indicates pre (#1) or post (#2) catalytic converter sensor.
Diagnostic Significance:
- Catalytic Converter Monitoring: Catalyst temperature is critical for monitoring catalytic converter operation and preventing overheating damage.
- Efficiency and Overheating: High temperatures can indicate converter overheating or reduced efficiency.
- Sensor Location and Bank Identification: Bank and sensor numbers are important for identifying specific sensor locations.
Diesel Aftertreatment Status
Description: A hybrid data point for diesel aftertreatment systems (Diesel Particulate Filter – DPF, NOx adsorber), reporting:
- Current DPF Regeneration Status (Active/Not Active)
- Current DPF Regeneration Type (Passive/Active)
- NOx Absorber Regen Status (Active/Not Active)
- NOx Absorber Desulfurization Status (Active/Not Active)
- Normalized Trigger for DPF Regen (0% complete, 100% start)
- Average Time Between DPF Regens
- Average Distance Between DPF Regens
Diagnostic Significance:
- DPF Regeneration Monitoring: Provides comprehensive status of DPF regeneration processes (active, passive, forced), trigger levels, and regeneration history.
- NOx Absorber Status: Monitors NOx adsorber regeneration and desulfurization status.
- Aftertreatment System Health: Helps assess the overall health and performance of diesel aftertreatment systems.
Diesel Exhaust Fluid Sensor Data
Description: Reports information from the Diesel Exhaust Fluid (DEF) sensor:
- DEF Type (Urea too high/low, Straight diesel, Proper DEF, Sensor fault)
- DEF Concentration (Urea concentration, ~32.5% for proper DEF)
- DEF Tank Temperature
- DEF Tank Level (may not be progressive, see NOx Control System notes)
Diagnostic Significance:
- DEF Quality and Level Monitoring: Crucial for monitoring DEF quality, concentration, tank level, and temperature in diesel SCR systems.
- SCR System Diagnostics: Data helps diagnose issues related to DEF quality, sensor malfunctions, and DEF supply to the SCR system.
- Tank Level Interpretation: Note that DEF tank level readings may not always be continuous and progressive.
Diesel Particulate Filter (DPF) & Diesel Particulate Filter (DPF) Temperature
Description:
- Diesel Particulate Filter (DPF): Reports: Inlet pressure, Outlet pressure, Differential pressure across the DPF (for up to three data points). Bank 1 vs 2 indicates engine side.
- Diesel Particulate Filter (DPF) Temperature: Reports: Inlet temperature, Outlet temperature (for up to two data points per exhaust bank). Bank 1 vs 2 indicates engine side.
Diagnostic Significance:
- DPF Clogging Monitoring: Differential pressure increase indicates soot accumulation and potential DPF clogging.
- Regeneration Needs: High differential pressure can signal an upcoming DPF regeneration event.
- Temperature Monitoring: DPF temperature data is essential for monitoring regeneration temperatures and preventing DPF damage from overheating.
NOx Sensor & NOx Sensor Corrected Data
Description:
- NOx Sensor: Reports NOx concentration levels (ppm) for up to four sensors: Bank 1/2 Sensor 1/2. Bank # indicates engine side, Sensor # indicates pre (#1) or post (#2) NOx adsorber.
- NOx Sensor Corrected Data: NOx concentration in PPM with learned adjustments and offsets applied.
Diagnostic Significance:
- NOx Emission Monitoring: NOx sensor data is essential for monitoring NOx emissions and the effectiveness of NOx reduction systems (SCR, NOx adsorber).
- Sensor Location Identification: Bank and sensor numbers are crucial for identifying sensor locations in multi-sensor systems.
- Data Correction: “NOx Sensor Corrected Data” provides a more accurate NOx reading after sensor calibration and adjustments.
NOx Control System
Description: Reports data on the NOx adsorption system (SCR):
- Average Reagent Consumption Rate (over previous 48 hours or 15L DEF)
- Average Demanded Consumption Rate (ECM commanded, over previous 48 hours or 15L DEF)
- Reagent Tank Level (0-100%, may not be progressive)
- NOx Warning Indicator Time (engine run time since NOx warning light activation)
Diagnostic Significance:
- SCR System Performance: Provides data on reagent (DEF) consumption, tank level, and warning light status for SCR systems.
- Reagent Consumption Issues: Discrepancies between average and demanded consumption rates can indicate SCR system problems.
- Tank Level Interpretation: Tank level readings may be discrete steps rather than continuous. Refer to description for interpretation.
- Warning Light History: “NOx Warning Indicator Time” tracks how long the NOx warning light has been active.
NOx NTE Control Area Status & PM NTE Control Area Status
Description: NTE (Not-To-Exceed) control area status for NOx and Particulate Matter (PM) emissions. Reports:
- Vehicle operating inside/outside NOx/PM control area.
- Vehicle in manufacturer exception/”carve-out” region.
- NTE related deficiency within NOx/PM control area.
Diagnostic Significance:
- Emissions Compliance Monitoring: NTE status indicates whether the vehicle is operating within emissions compliance limits under specific engine operating conditions (speed and load).
- Exemption/Carve-out Regions: Indicates if the vehicle is operating within manufacturer-defined exempt regions where NTE limits may not apply.
- Deficiency Detection: Identifies NTE-related emissions deficiencies.
PM Sensor Bank 1 & 2 & Particulate Matter (PM) Sensor
Description:
- PM Sensor Bank 1 & 2: Reports for banks 1 & 2: PM sensor active (yes/no), PM sensor regenerating (yes/no), PM sensor value (0% clean, 100% regen required).
- Particulate Matter (PM) Sensor: Soot concentration (mg/m3) measured by PM sensors on banks 1 & 2.
Diagnostic Significance:
- Particulate Matter Monitoring: Provides data on particulate matter (soot) levels in the exhaust.
- PM Sensor Status: Indicates sensor activity, regeneration status, and PM accumulation levels.
- DPF Performance: PM sensor data is related to Diesel Particulate Filter performance and soot loading.
SCR Inducement System & NOx Warning And Inducement System
Description: Parameters related to Selective Catalytic Reduction (SCR) inducement strategies (driver alerts and functional restrictions for SCR system issues).
- SCR Inducement System: Reports current SCR inducement status (on/off) and reasons (low reagent, incorrect reagent, abnormal consumption, excessive NOx). Also reports inducement history in 10,000 km blocks.
- NOx Warning And Inducement System: Reports warning/inducement levels (Level 1/2/3 – severity levels) and status (Inactive, Enabled but not active, Active, Not Supported). Also reports total engine hours for various incorrect reagent/operation conditions.
Diagnostic Significance:
- SCR System Fault Indication: “SCR Inducement System” and “NOx Warning And Inducement System” provide detailed information about SCR system faults that trigger driver warnings and potential vehicle performance restrictions (inducement).
- Inducement Level and Reason: Indicates the severity of the inducement and the underlying cause (DEF level, quality, NOx emissions, etc.).
- Fault History Tracking: Tracks inducement history over distance intervals and engine run time for specific fault conditions.
Engine Run Time for AECD
Description: Reports total engine run time (seconds) for each Auxiliary Emissions Control Device (AECD) that was active. AECDs can temporarily disable emissions control components under specific conditions (permitted but must be justified to regulatory bodies).
Diagnostic Significance:
- AECD Operation Monitoring: Tracks the total operating time of each AECD.
- Emissions Control System Behavior: Provides insight into when and how often AECDs are active, which can be relevant to emissions control system analysis.
- Device Identification: Lists AECDs by number. Factory manual may be needed for AECD-specific information.
- Timer Types: AECD timers may track total active time or differentiate between emissions control inhibition levels (up to 75% vs. beyond 75%). Timers cannot be reset.
This Eobd Obdii Live Data Manual provides a detailed overview of essential parameters for automotive diagnostics. By understanding and utilizing this live data, technicians and enthusiasts can gain valuable insights into vehicle operation, diagnose issues effectively, and ensure optimal vehicle performance and emissions control. Mastering EOBD OBDII live data is a key skill in modern automotive repair and maintenance.
