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.

IMPORTANT: You must perform the Circuit/System Verification first.

Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description .
Ignition ON, verify the scan tool hood position parameter displays Open.
- If the hood position does not display Open, refer to Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.
Disconnect the VLOM harness connector.
Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal E and ground.
- If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test or replace the VLOM assembly.
Verify that a test lamp does not illuminate between the ignition circuit terminal E and the affected control circuit terminal.
- If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
Remove the test lamp.
Command the affected cylinder deactivation solenoid ON with a scan tool. Verify with a scan tool that the affected cylinder deactivation solenoid Ckt. Short Volts Test Status parameter is OK.
- If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
Install a 3A fused jumper wire between the affected control circuit terminal and the ignition circuit terminal E. Command the affected cylinder deactivation solenoid ON with a scan tool. Verify with a scan tool that the affected cylinder deactivation solenoid Ckt. Short Volts Test Status parameter is displaying Fault.
- If not the specified value, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
If all the circuits test normal, test or replace the VLOM assembly.