Buick EBCM Won't Communicate

Some owners of 2008-2015 Buick Enclave vehicles may comment that the ABS and red brake lamp is on in the instrument panel. When trying to retrieve DTCs, the scan tool might not communicate with the EBCM.

The scan tool may communicate with all other high and low speed GM LAN modules and some may have set DTC U0121 against the EBCM. While performing normal diagnostics, it will be found that the power circuits, ground circuits, communication enable signal circuit and the GM LAN circuits going to the EBCM test good. This testing may lead to replacement of the EBCM. However, the concern may still be present after installing a new EBCM.

The concern may be caused by one of the following issues:

1. If equipped with StabiliTrak, the yaw and lateral accelerometer (Multi-Axis) sensor or the steering wheel angle sensor supply voltage (circuit 2087, dark green) shorted and is pulling down the internal circuitry of the EBCM. Not all vehicles use circuit 2087 to supply voltage to the steering wheel angle sensor, so be sure to check service information for the specific vehicle. If circuit 2087 is backed out of the EBCM connector and communications returns, inspect for either this circuit being shorted to ground or for a sensor concern.
2. A shorted WSS (wheel speed sensor) or WSS wiring. In many cases, this is found on vehicles that have aftermarket lift kits, wheel bearings and/or WSS wiring. Inspect the WSS sensor wiring for any broken/shorted/chaffed circuits. If none are found, unplug the WSS one at a time and see if communication returns. If so, repair and/or replace any wiring connector and/or WSS issues.