Circuit/System Testing
WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.
- Disconnect the transmission X176 24-way connector. Ignition ON. The scan tool IMS Status parameter should display HI for the R1, R2, D1, D2 and S signal circuit displays.
- If a signal displays LOW, disconnect the PIM connector X1 and test the circuit for a short to ground.
- If the circuit tests normal, replace the PIM.
- Install DT-48493
to the vehicle harness connector X176. See Special Tools . Verify that a test lamp illuminates between the Direction IMS switch ground circuit and battery positive.
- If the test lamp does not illuminate, disconnect PIM connector X1 and test the ground circuit for an open, high resistance or short to voltage condition.
- If the circuit tests normal, replace the PIM.
- Connect a 3-amp fused jumper wire between each Direction IMS signal circuit at DT-48493
and the ground circuit terminal. See Special Tools . The scan tool parameter should display LOW for each signal circuit when grounded.
- If a scan tool parameter always displays HIGH, disconnect PIM connector X1 and test the circuit for an open, high resistance or short to voltage condition.
- If the circuit tests normal, replace the PIM.
- Disconnect the transmission 16-way X175 connector. Install DT-47825-10
to the vehicle harness. See Special Tools . Connect a 3-amp fused jumper wire between the Starter signal circuit terminal and ground. The scan tool parameter should display LOW when the signal circuit is grounded.
- If the scan tool parameter always displays HIGH, disconnect PIM connector X1 and test the circuit for an open, high resistance or short to voltage condition.
- If the circuit tests normal, replace the PIM.
- Disconnect the IMS connector at the switch.
- Test the direction signal circuits and the ground circuit between the IMS and the transmission 24-way X176 connector for a short to ground, open, high resistance or short to voltage condition.
- Test the Starter signal circuit between the IMS and the transmission 16-way X175 connector for a short to ground, open, high resistance or short to voltage condition. The TCM is a pass-through of the Starter signal circuit and should be tested as a typical circuit path.
- If the circuit, including the TCM, tests normal, replace the IMS switch.
IMPORTANT: Connect one end of the DT-48493 to the transmission connector. See Special Tools . Use the other end as the terminal testing point.IMPORTANT: Connect one end of the DT-47825-10 to the transmission connector. See Special Tools . Use the other end as the terminal testing point.
IMPORTANT:
The remaining diagnostic steps test the internal transmission components and circuits. The automatic transmission fluid pan assembly must be removed in order to perform the diagnostic tests.