An owner of a 2008-2015 Buick Enclave may comment about the ABS and red brake lamp on. When trying to retrieve DTCs, the technician’s scan tool may 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 a U0121 DTC against the EBCM. 

While performing normal diagnostics, you may find that the power circuits, ground circuits, communication enable circuit and the GM LAN circuits going to the EBCM test are good.

This testing may lead to EBCM replacement. However, the concern may still be present after installing a new EBCM.

If equipped with StabiliTrak, the yaw and lateral accelerometer sensor or the steering wheel angle sensor supply voltage (circuit 2087, dark green) may have shorted and pulled down the EBCM internal circuitry. (Note that 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 communication returns, inspect for either this circuit being shorted to ground or for a sensor concern. Check for a shorted WSS or WSS wiring problem.