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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1593 (Trailer Brake Control System) >> Diagnostic Information and Procedures >> DTC C0870, C1112, C1113, C1114, or C1119 (Gasoline Without LY6) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: These diagnostics are based on having no trailer connected.
  1. Ignition ON, verify that DTC P2534 is not set.
  2. Ignition OFF, disconnect the harness connector at the trailer brake control relay.
  3. Test for less than 5 Ω between the ground circuit terminal B and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition OFF, verify that a test lamp illuminates between the B+ circuit terminal F and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the STUD 2 fuse is open, replace the trailer brake control relay.
  5. Ignition ON, verify that a test lamp does not illuminate between control circuit terminal E and ground.
    • If test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
  6. Ignition ON, verify that a test lamp does not illuminate between control circuit terminal E and B+.
    • If test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the fuel pump/trailer brake control module.
  7. Ignition ON, test for 3.2-4.1 V between the control circuit terminal C and ground.
    • If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fuel pump/trailer brake control module.
    • If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
  8. Ignition ON, test for 3.2-4.1 V between the control circuit terminal A and ground.
    • If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fuel pump/trailer brake control module.
    • If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
  9. Ignition ON, test for less than 1 V between the control circuit terminal D and ground.
    • If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
  10. If all circuits test normal, replace the trailer brake control relay.
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