- Powertrain/On-Board Diagnostic System Check

The Powertrain OBD System check is an organized approach to identifying a problem created by an electronic engine control system malfunction. The Powertrain OBD system check must be the starting point for any driveability complaint diagnosis, because it directs the service technician to the next logical step in diagnosing the complaint. Understanding the table and using it correctly will reduce diagnostic time and prevent the replacement of good parts.

DO NOT perform this check if a driveability complaint is not present.

This vehicle is equipped with a Powertrain Control Module (PCM) utilizing an Electrically Erasable Programmable Read Only Memory (EEPROM). When diagnostics call for replacement of the PCM the replacement PCM must be programmed.

Inspect all related wiring and connections including the connections at the PCM. These may cause an intermittent malfunction. Check for damaged, corroded or pushed out terminals.


TEST DESCRIPTION
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The Powertrain OBD System Check should not be performed unless one of the concerns noted is present, failure to follow this procedure could lead to misdiagnosis of the system.
2. Checking if the PCM and scan tool can communicate.
3. Checking if the vehicle will start and run.
4. Check for DTCs that are currently set. Check for bulletins before proceeding with further diagnosis. If more than one DTC is set diagnose DTCs in the following order:
^ PCM memory or fault DTCs (P0601, P0602, P0606).
^ System and Ignition voltage DTCs.
^ Component / circuit DTCs (sensors, etc.).
^ System DTCs (MAF System Performance, TP System Performance, etc.).
- If more than one DTC is set in any group, diagnose DTC's from the lowest number to the highest number.
- First failures of Type B DTCs will store in Test Failed Since Code Clear but not in History.When the DTC is indicated in both Last Test Failed and History this indicates a current fault.
- Before diagnosing a DTC that is only stored in history check the odometer information (stored in Freeze Frame or Failure Records) to verify that the DTC is a recent fault.
- Since 3 consecutive passing drive trips are needed to turn OFF the MIL on some DTCs, use the DTC Status display to determine if a Type A DTC has tested and passed this ignition cycle.
- Always store the scan data from DTCs that are set before proceeding to the DTC Table. Use the Capture Info function of the scan tool or write down the scan data for future reference.
- Refer to Automatic Transmission/Transaxle for those DTC's.
5. Check for bulletins before proceeding with further diagnosis. If actual and typical scan data values are different and a fault is suspected check the DTC information for that component or system and verify that it's related DTCs have tested. If they have tested use the sensor information to help diagnose suspected sensor faults or if a system fault is suspected (EGR operation, HO2S operation, etc.) refer to the DTC that applies to the suspected system and if possible use the diagnostic table to aid in diagnosis. Testing and Inspection