Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Yukon and 2009 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

Ignition OFF, disconnect the ECM connector (X3).
Ignition ON, measure the voltage on the harness of the ECM connector (X3-66) for 5 V.
- If you have 5 V, test or replace the ECM.
- If the value is other than 5 V, test harness for:
  - Short to Voltage
  - Short to Ground
  - Open
If no trouble found, replace the TCM.