The following procedure has been established to assist technicians in the field with enabling and running OBD-II Monitors on RWD/4WD trucks and Jeep models equipped with Jeep/Truck Engine Controller (JTEC). The order listed in the following procedure is intended to allow the technician to effectively complete each monitor and to set the CARB Readiness Status in the least time possible.
By performing a battery disconnect, or erasing diagnostic trouble codes, the CARB Readiness and all additional OBD information will be cleared.
The following is an outline of the Monitoring Run Process, including suggestions and tips in order to aid in the process of meeting the enabling criteria for these monitors. The most efficient order has been outlined below. For example, the first two monitors have very similar enable criteria; it is possible that the Evaporative Leak Detection Monitor will run during the O2 Sensor Heater Monitor.
This monitor requires a cold start, usually an overnight soak or parked for at least 8 hours without the engine running. The engine coolant temperature must be within 10 degrees of ambient/battery temperature, and the sensed Ambient (outside) Temperature must be between approximately 40°F and 90°F.
Misfire monitor is continuously running during engine operation. For the Misfire monitor to be enabled, the Adaptive Numerator must be learned since battery disconnect and every Key on there after (known as Power-on learning).
To allow the PCM to learn the Adaptive Numerator, the following must happen:
Open Throttle. Engine Cool Temp Above 100°F Or If Below 100°F, Wait For ECT Rise Of 59°F.
This monitor requires a cold start, usually an overnight soak or parked for at least 8 hours without the engine running. The engine coolant temperature must be within 10 degrees of ambient/battery temperature, and the sensed Ambient (outside temperature) must be between approximately 0°F and 100°F. The monitor should run directly after starting the engine.
The vehicle will need to be driven at a steady highway speed for a few minutes. The monitor will typically enable and start running at approximately 35 to 40 MPH for 2.5L and 4.0L engines, 50 to 60 MPH for all others). If the vehicle is equipped with a manual transmission, using 4th gear may assist in meeting the monitor running criteria.
The vehicle will need to be driven for a period of time at a steady highway speed. Approximately 35 to 40 MPH for 2.5L and 4.0L engines, 50 to 60 MPH for all others and brought to a stop for a short period of time with the A/T left in Drive. The O2 Monitor will not run in Park or Neutral, except for vehicles equipped with a M/T.
The Purge Free cells must be updated before the monitor will run. The enabling conditions are similar to the O2 Sensor Monitor enabling conditions such as, the vehicle will need to be driven for a period of time at highway speeds and brought to a complete stop. The Purge Flow Monitor will attempt to run every OTHER throttle closure. If all of the parameters are met and it still does not run, with your foot firmly on the Brake, quickly open and close the throttle, this will allow another Purge Free update, and then the Purge Flow Monitor should run.
The Adaptive Numerator is a software learning routine that tells the PCM where the crankshaft slots are. Since every crankshaft is different, the PCM must learn exactly where its particular crankshaft slots are; otherwise its RPM calculations would be wrong. After a battery disconnect and then a power-up of the PCM, the Adaptive Numerator is set to a value which it would be at if everything were perfect (crankshaft slots, sensors, PCM hardware, etc.). If the Adaptive Numerator is equal to the default value, no learning has happened and the Misfire Monitor will not run.
Hope this helps.