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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1339 (Trailer Brake Control System) >> Diagnostic Information and Procedures >> DTC C0880, C0890, C1115, C1116, C1117, or C1118 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the trailer brake controller switch.
  2. Test for less than 5 ohms of resistance between the low reference circuit terminal 8 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the TBCM.
  3. Ignition ON, test for 4.8 - 5.2 volts between the 5-volt reference circuit terminal 3 and ground.
    • If less than the specified range, test the 5-volt reference 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 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the TBCM.
  4. Verify the scan tool Manual Apply Switch parameter is less than 5 percent.
    • If greater than the specified range, test the signal circuit terminal 4 for a short to voltage. If the circuit tests normal, replace the TBCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal 4 and the 5-volt reference circuit terminal 3. Verify the scan tool Manual Apply Switch parameter is greater than 90 percent.
    • If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
  6. Verify the scan tool Redundant Manual Apply Switch parameter is greater than 90 percent.
    • If less than the specified range, test the signal circuit terminal 5 for a short to voltage. If the circuit tests normal, replace the TBCM.
  7. Install a 3A fused jumper wire between the signal circuit terminal 5 and the 5-volt reference circuit terminal 3. Verify the scan tool Redundant Manual Apply Switch parameter is less than 2 percent.
    • If greater than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TBCM.
  8. Ignition ON, test for 4.8 - 5.2 volts between the signal circuit terminal 6 and ground.
    • If less than the specified range, test the signal 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 signal circuit for a short to voltage. If the circuit tests normal, replace the TBCM.
  9. If all circuits test normal, test or replace the trailer brake controller switch panel.
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