On-Board Diagnostics: Notes
The PCM has been programmed to monitor many different circuits of the fuel injection system. This monitoring is called on-board diagnosis.
Certain criteria, or arming conditions, must be met for a trouble code to be entered into the PCM memory. The criteria may be a range of: engine RPM, engine temperature, and/or input voltage to the PCM. If a problem is sensed with a monitored circuit, and all of the criteria or arming conditions are met, then a trouble code will be stored in the PCM.
It is possible that a trouble code for a monitored circuit may not be entered into the PCM memory even though a malfunction has occurred. This may happen because one of the trouble code criteria have not been met.
The PCM compares input signal voltages from each input device with specifications (the established high and low limits of the range) that are programmed into it for that device. If the input voltage is not within specifications and other trouble code criteria are met, a trouble code will be stored in the PCM memory.
The On Board Diagnostics have evolved to the second Generation of Diagnostics referred to as OBDII/EOBD. These OBDII/EOBD Diagnostics control the functions necessary to meet the requirements of California OBDII, Federal OBD regulation and European regulation. These requirements specify the inclusion of a Malfunction Indicator Light (MIL) located on the instrument panel. The purpose of the MIL is to inform the vehicle operator in the event of a malfunction of any emission system or component.
MIL Lamp Strategy
I/M Readiness OK to test = Key On Engine OFF
- MIL Lamp will remain on until the vehicle is started or Ignition is turned off.
I/M not ready for testing = Key On Engine OFF
- MIL Lamp on solid for (15) seconds then MIL Lamp will flash on/off for (5) seconds then it will remain on until the vehicle is started or the Ignition is turned off.
OBDII Monitor Run Process
The following procedure has been established to assist Technicians in the field with enabling and running OBDII Monitors. 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.
**NOTE**
- Once the monitor run process has begun, do not turn off the ignition. By turning the ignition key off, monitor enabling conditions will be lost. NVLD Monitor runs after key off.
- By performing a Battery Disconnect, or Selecting Erase DTCs, the CARB Readiness and all additional OBDII information will be cleared.
Monitor Preliminary Checks:
- Plug a DRBIII® into the vehicle's DLC.
- Turn the ignition, KEY ON-ENGINE OFF. Watch for MIL lamp illumination during the bulb check. MIL lamp must have illuminated, if not, repair MIL lamp.
- On the DRB III® Select #1 DRB III Standalone.
- Select #1 1998-2005 Diagnostics
- Select #1 Engine
- Select #2 DTCs and Related Functions
- Select #1 Read DTCs
- Verify that No Emissions Related DTCs are Present.
- If an Emissions DTC is Present, the OBD II Monitors may not run and the CARB Readiness will not update.
- The Emissions related DTC, will need to be repaired, then cleared. By clearing DTCs, the OBD Monitors will need to be run and completed to set the CARB Readiness Status.
- Return to Engine Select Function Menu and Select #9, OBD II Monitors.
- Select #3 CARB Readiness Status.
Do all the CARB Readiness Status Locations read
YES?
*YES , then all monitors have been completed and this vehicle is ready to be I/M or Emission Tested.
*NO , then the following procedure needs to be followed to run/complete all available monitors.
**NOTE**
- Only the monitors, which are not YES in the CARB Readiness Status, need to be completed.
- Specific criteria need to be met for each monitor. Each monitor has a Pre-Test screen to assist in running the monitor.
For additional information, refer to the Chrysler Corporation Technical Training Workbook titled On Board Diagnostics: OBDII/EOBD , part number 81-699-01050.
The most efficient order to run the monitors has been outlined below, including suggestions to aid the process.