Circuit/System Testing

WARNING: This page is about a different car, the 2008 Isuzu i-370, 2008 Isuzu i-290, 2008 GMC Canyon, and 2008 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.

Using the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.
Ignition OFF, disconnect the harness connector of the module that is not communicating.
Ignition ON, verify that a test lamp illuminates between all battery positive voltage circuits and ground.
- If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module.
Verify that a test lamp illuminates between all ignition voltage circuits and ground.
- If the test lamp does not illuminate, test the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module.
Test for less than 1 ohm between the module ground circuits and ground.
- If greater than 1 ohm, repair the ground circuit for open/high resistance.
Test for less than 1 ohm in the GMLAN serial data circuit(s) between the non-communicating module and the module that displays the DTC.
- If greater than 1 ohm, test the GMLAN serial data circuit(s) for open/high resistance.
If all circuits test normal, replace the module that is not communicating.