Circuit/System Testing
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition ON, verify the scan tool GPCM Ignition 1 Signal parameter is battery voltage.
- If the Ignition 1 Signal parameter is not battery voltage, test the battery positive voltage circuit to the glow plug control module for an open or short to ground. If the circuit tests normal, replace the GPCM.
- Ignition OFF, disconnect the X2 harness connector at the GPCM.
- Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 52 and ground.
- If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the GPCM.
- Ignition ON, verify that a test lamp illuminates between the ignition 0 voltage circuit terminal 53 and ground.
- If the test lamp does not illuminate, test the ignition 0 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the GPCM.
- If all circuits test normal, replace the GPCM.