Ensuring your Chrysler, Dodge, Jeep, or Plymouth vehicle passes emissions testing requires understanding OBDII readiness monitors and performing the correct drive cycle. For vehicles equipped with a JTEC PCM (Powertrain Control Module), setting these monitors efficiently is crucial for automotive technicians. This guide provides a comprehensive breakdown of the Chrysler drive cycle for JTEC PCM vehicles, focusing on achieving OBDII readiness quickly and effectively.
Understanding OBDII Readiness Monitors on Chrysler JTEC PCMs
OBDII (On-Board Diagnostics II) systems utilize readiness monitors to self-test critical emission control systems. These monitors run diagnostic checks to ensure components are functioning correctly. When monitors are “ready,” it signifies the system has been tested and passed. If monitors are “not ready,” the vehicle may fail an emissions test. Clearing diagnostic trouble codes (DTCs) or disconnecting the battery resets these monitors to a “not ready” state, necessitating a drive cycle to reset them. The JTEC PCM, common in many Chrysler vehicles of the late 90s and early 2000s, requires specific driving patterns, known as drive cycles, to enable and run these monitors.
Chrysler Drive Cycle Procedure for OBDII Readiness Monitors
The following outlines the recommended drive cycle procedure to enable OBDII monitors on Chrysler vehicles with JTEC PCMs. This sequence is designed to be efficient, allowing technicians to set the CARB (California Air Resources Board) Readiness Status in minimal time.
General Tips for Monitor Run Process:
- Cold Start: Begin the drive cycle with a cold start. Ideally, the vehicle should sit overnight or for at least 8 hours to ensure engine coolant temperature is within 10 degrees of the ambient/battery temperature. The ambient temperature should be between approximately 40°F and 90°F.
- Avoid Interruptions: Once the monitor run process begins, do not turn off the ignition. Turning the key off can interrupt the process and reset enabling conditions (except for the O2 Heater Monitor, which runs after key off).
- No Battery Disconnect or Code Clearing: Avoid battery disconnection or erasing DTCs before or during the drive cycle, as this will clear CARB Readiness and all OBD information, requiring the process to restart.
Evaporative Leak Detection Monitor (LDP System Equipped Vehicles)
- Conditions: Cold start (as described above). Engine coolant temperature within 10°F of ambient/battery temperature. Ambient temperature between 40°F and 90°F.
- Procedure: This monitor often runs passively during the initial stages of the drive cycle, particularly while meeting conditions for the Catalyst Monitor. No specific driving action is solely dedicated to this monitor beyond the cold start condition.
Catalyst Monitor
- Conditions: Steady highway speed driving.
- Procedure: Drive at a steady speed between 45 and 60 mph for several minutes under normal driving conditions. For manual transmission vehicles, using 4th gear can assist in meeting the monitor running criteria.
EGR Monitor
- Conditions: Closed loop operation. Coolant temperature above 170°F. Stable driving conditions with minimal fluctuation in TPS (Throttle Position Sensor), MAP (Manifold Absolute Pressure), MPH, and RPM.
- Procedure: Maintain a constant speed and throttle input on a level road once the engine is warmed up and in closed loop. Smooth driving is key to allow this monitor to complete.
O2 Sensor Monitor
- Conditions: Highway speed driving followed by a complete stop. Automatic transaxle in Drive.
- Procedure: Drive at highway speeds for a period, then come to a complete stop with the automatic transmission in Drive. Ensure the vehicle is not in Park or Neutral, as the O2S Monitor will not run in these modes on automatic transmission vehicles.
Purge Monitor
- Conditions: Similar to O2 Sensor Monitor. Purge Free cells must be updated.
- Procedure: Drive at highway speeds and then come to a complete stop. The Purge Flow Monitor attempts to run every other throttle closure. If it doesn’t run, with your foot firmly on the brake, quickly open and close the throttle. This action can trigger a Purge Free update, after which the Purge Flow Monitor should initiate.
O2 Sensor Heater Monitor
- Conditions: Highway speed driving to arm the monitor. Hot soak after vehicle operation.
- Procedure: Drive at highway speeds to meet enabling conditions. After driving, allow the vehicle to hot soak for a few minutes with the ignition off before checking monitor status. Avoid turning the key on prematurely, as this will abort the test, and the drive cycle to arm the monitor will need to be repeated.
Mis-fire Monitor
- Conditions: Continuously running during engine operation. Adaptive Numerator must be learned after battery disconnect or PCM power-up.
- Adaptive Numerator Learning: This is crucial for misfire monitor operation. To allow the PCM to learn the Adaptive Numerator:
- Open throttle.
- Engine Coolant Temp above 100°F (or wait for a 59°F rise if below 100°F).
- More than 10 inches of vacuum.
- Above 1200 RPM.
- Below 3000 RPM (ATX) / 3488 RPM (MTX).
- Procedure: Normal driving under the conditions above will allow the PCM to learn the Adaptive Numerator, enabling the Mis-fire Monitor to run continuously.
Fuel System Monitor
- Conditions: Continuously running during engine operation.
- Procedure: This monitor operates continuously during normal driving. No specific drive cycle actions are typically required solely for the Fuel System Monitor to run, provided the engine is operating within its normal parameters.
Conclusion
Successfully completing a Chrysler drive cycle for JTEC PCM vehicles and setting OBDII readiness monitors requires attention to detail and adherence to specific procedures. By following these guidelines for each monitor, automotive technicians can efficiently ensure vehicles are ready for emissions testing, saving time and providing accurate diagnoses. Understanding the nuances of each monitor’s enabling criteria is key to a smooth and successful process.
