Automatic Transmission/Transaxle: Testing and Inspection
Diagnostic Chart:
Wiring Diagram:
Circuit Description
The Powertrain OBD system check is an organized approach which is used in order to identify a problem which is created by an electronic engine control system malfunction. The Powertrain OBD system check is the starting point for any driveability concern diagnosis, because it directs the service technician to the next logical step in diagnosing the concern. 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 concern is not present.
Diagnostic Aids
Inspect all related wiring and connections including the connections at the PCM. An intermittent malfunction may be caused by poor electrical connections. Check the electrical terminals for any of the following conditions:
^ Damaged
^ Corroded
^ Pushed out terminals
Test Description
The numbers below refer to the step numbers in 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 a misdiagnosis of the system.
2. The MIL should be on steady with the key ON and the engine OFF.
3. Checking if the PCM and the scan tool can communicate.
4. This step checks if the vehicle starts.
5. Before proceeding to the applicable DTC table, check for related service bulletins.
If multiple DTCs are stored, refer to the DTC tables by using the following priority:
^ PCM error DTCs (P0601, P0603).
^ System voltage DTCs.
^ Component level DTCs (sensors, switches, relays, output drivers, etc.).
^ System level DTCs (TP system performance, Misfire, Fuel trim, HO2S low or high, etc.).
- First failures of Type B DTCs will store in Test Failed Since Code Cleared (Test Fail SCC) but not in History. When the MIL is ON and a DTC is indicated in History, this indicates a current fault.
If the scan tool is unable to record the DTC information, then record this information on paper.
6. This step detects a MIL circuit shorted to ground.
7. Check for related service bulletins before proceeding to Symptoms or Components. The diagnostic tables are designed for use with a properly functioning scan tool. If a malfunctioning scan tool is suspected, connect the scan tool to another vehicle in order to verify the operation. The serial data communications must be corrected before beginning any other diagnostic procedure. The OBD II serial data may not transmit if the system voltage is below 9.0 volts or above 16.0 volts. DO NOT clear the DTCs unless directed by a diagnostic procedure. Clearing the DTCs will also clear any valuable Freeze Frame data.