Decoding the OBDII Error Code P0107: MAP/Barometric Pressure Circuit Low Input

Navigating the complexities of your vehicle’s onboard diagnostics system can be daunting, especially when faced with error codes. Among these, the EOBD/OBDII error code P0107, signaling “Manifold Absolute Pressure/Barometric Pressure Circuit Low Input,” is a common concern for vehicle owners and mechanics alike. This article delves into the intricacies of the P0107 code, providing a comprehensive understanding of its meaning, symptoms, potential causes, and effective troubleshooting steps.

Understanding the P0107 Code: Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

The P0107 diagnostic trouble code is a generic powertrain code that applies across vehicles equipped with OBD-II systems. It indicates an issue within the Manifold Absolute Pressure (MAP) or Barometric Pressure sensor circuit. The MAP sensor plays a crucial role in your engine’s performance by measuring the pressure within the intake manifold. This sensor communicates with the Powertrain Control Module (PCM) to ensure optimal fuel delivery and ignition timing.

The MAP sensor typically receives a 5-volt reference signal from the PCM. Internally, a resistor within the sensor responds to pressure changes, altering the voltage signal sent back to the PCM. This voltage signal usually ranges from approximately 1 volt (high vacuum/low pressure) to 4.5 volts (low vacuum/high pressure), reflecting engine load. The P0107 code is triggered when the PCM detects that the MAP sensor signal voltage drops below a critical threshold, generally around 0.25 volts, indicating a “low input” condition.

Symptoms Associated with a P0107 Error Code

When the PCM detects a low signal from the MAP sensor, it can significantly impact engine operation. The most immediate symptom is often difficulty starting the vehicle. Beyond this, other symptoms may include:

• Hard starting: The engine struggles to ignite and turn over.
• Extended cranking: The engine takes longer than usual to start.
• Engine sputtering or misfiring: Irregular combustion leading to rough engine running.
• Black smoke from exhaust: Indicates excessively rich fuel mixture.
• Reduced fuel efficiency: Engine inefficiency due to incorrect fuel metering.
• Intermittent engine stalling: The engine may suddenly stop running.
• Malfunction Indicator Lamp (MIL) illumination: The check engine light will illuminate on the dashboard.

Potential Causes of a P0107 Code

Several factors can lead to a low input signal in the MAP sensor circuit, triggering the P0107 code. These can range from sensor malfunctions to wiring issues:

• Faulty MAP sensor: The sensor itself may be defective and providing inaccurate readings.
• Signal circuit issues: An open or short circuit in the wiring connecting the MAP sensor signal wire to the PCM.
• 5-Volt reference circuit problems: An open or short circuit in the 5-volt reference wire supplying power to the MAP sensor.
• Ground circuit issues: An open or short circuit in the ground wire for the MAP sensor.
• PCM malfunction: In rare cases, a problem within the PCM itself can cause incorrect voltage readings or reference voltage issues.

Diagnosing and Resolving the P0107 Error Code

Troubleshooting a P0107 code requires a systematic approach, often involving a scan tool and a digital multimeter (DVOM). Here’s a step-by-step diagnostic process:

1. Initial Voltage Check: With the ignition key turned to the “ON” position and the engine off, use a scan tool to monitor the MAP sensor voltage. A reading below 0.5 volts is a strong indicator of a problem.

2. 5-Volt Reference Verification: Disconnect the MAP sensor connector. Using a DVOM, check for the presence of a 5-volt reference signal at the MAP sensor connector.

   • If 5 Volts is absent: Check for the 5-volt reference at the PCM connector.
     • If present at PCM but not MAP connector: Repair an open circuit in the reference wire between the PCM and MAP sensor.
     • If absent at PCM connector: Investigate PCM power and ground connections. Repair or replace PCM as necessary. (Note: In some vehicles, particularly Chrysler models, a shorted sensor on the 5-volt reference circuit, like a Crank sensor or Vehicle Speed Sensor, can cause a voltage drop. Disconnect sensors one by one to isolate a shorted sensor if the 5V reference is missing).

3. Signal Circuit Test: If 5-volt reference is present at the MAP sensor connector, use a jumper wire to connect the 5-volt reference circuit to the signal circuit at the MAP sensor connector. Monitor the MAP voltage on the scan tool. It should now read approximately 4.5 to 5 volts.

   • If voltage reading is correct (4.5-5V): Replace the MAP sensor as it is likely faulty.
   • If voltage reading is still low: Repair a potential open or short circuit in the signal wire between the MAP sensor and the PCM. Re-check voltage.

4. Wiggle Test: If wiring appears sound, perform a “wiggle test.” Start the engine and gently manipulate the MAP sensor wiring harness and connector. Also, lightly tap on the MAP sensor itself. Observe the scan tool for any fluctuations in voltage or changes in engine speed. These changes can indicate intermittent wiring issues or a faulty sensor. Repair connectors, wiring, or replace the sensor as indicated.

5. Vacuum Test: If the wiggle test yields no results, use a vacuum pump (or carefully apply vacuum orally) to the MAP sensor vacuum port. As vacuum is applied, the MAP sensor voltage should decrease. With no vacuum, the sensor should read around 4.5 volts. If there is no change in the MAP sensor reading during this test, replace the MAP sensor.

Related OBD-II Trouble Codes: P0105, P0106, P0108, and P0109 are related MAP sensor diagnostic trouble codes that may indicate similar or related issues.

For further assistance and community support in diagnosing and resolving a P0107 error code, consider consulting online automotive forums or seeking professional diagnostic services.

Disclaimer: This information is for informational purposes only and is not intended as professional repair advice. Always consult a qualified technician for vehicle repairs. We are not responsible for any actions taken based on this information. All content is copyright protected.