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Communication Breakdown for Chevy Avalanche

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Some owners of 2007-2013 Chevy Avalanche vehicles may comment about the anti-lock brake system (ABS) and red brake lamp being on the instrument panel cluster. When trying to retrieve diagnostic trouble codes (DTCs), the scan tool may not communicate with the electronic brake control module (EBCM). The scan tool will 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, 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 the replacement of the EBCM. However, this concern may still be present after installing a new EBCM.

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

If equipped with StabiliTrak, the yaw and lateral accelerometer sensor or the steering wheel angle sensor supply voltage (circuit 2087...dark green) shorted and is pulling down the internal EBCM circuitry. 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. The circuit may be shorted under the passenger front seat at the rear camera module bracket. 

A shorted WSS or WSS wiring may be present. In many cases, this is found on full-size trucks and utilities 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 communications returns. 

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