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.

IMPORTANT: All electrical components and accessories must be turned OFF and allowed to power down.

Ignition OFF, disconnect the harness connector at the solid state relay module.
Test for less than 5 ohms of resistance between the ground circuit terminal B and ground.
- If greater than the specified range, test the ground circuit for an open/high resistance.
Ignition ON, test for 9 - 11 volts between the 10-volt control circuit terminal E and ground.
- If less than the specified range, test the 10-volt control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
- If greater than the specified range, test the 10-volt control circuit for a short to voltage. If the circuit tests normal, replace the TBCM.
Ignition OFF, reconnect the harness connector at the solid state relay module.
Connect a test lamp between the control circuit terminal C of the trailer connector and the ground circuit terminal B.
Command the trailer brake relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the TBCM.
- If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
If all circuits test normal, test or replace the trailer brake solid state relay (SSR).