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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1133 (Data Communication System) >> Diagnostic Information and Procedures >> DTC U0100 - U0117, U0121 - U0141, U0151 - U0160, U0164 - U0186, U0194 - U0214, U0230 - U0257, U0291 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Using the DTC Descriptor and Diagnostic Aids above, determine the control module that is not communicating.
  2. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
  3. Test for less than 1 U between the control module ground circuits and ground.
    • If greater than the specified range, test the ground circuit for an open/high resistance.
    NOTE: Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit, and the BCM is the output for these circuits. Refer to the control module schematics to identify which control modules have these circuits. If the control module that is not communicating is the BCM or does not have one of these circuits, proceed to step 5.
  4. Ignition ON, verify that a test lamp illuminates between the serial data communication enable circuit OR the accessory wakeup serial data circuit and ground.
    • If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
  5. Ignition ON, verify that a test lamp illuminates between all battery positive 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 control module for a short to ground. If the circuits test normal, replace the control module.
  6. 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 control module for a short to ground. If the circuits test normal, replace the control module.
  7. Test for less than 1 U on the GMLAN serial data circuits between the non-communicating control module and the control module that displays the DTC.
    • If greater than the specified range, test the serial data circuit for open/high resistance.
  8. If all circuits test normal, replace the control module that is not communicating.
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