Unable To Communicate With The EBCM DTC U0121 – 2007-2015 Buick Cadillac Chevrolet GMC Pontiac Saturn

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Subject:	Unable To Communicate With The EBCM DTC U0121
Models:	2008-2015 Buick Enclave
	2007-2014 Cadillac Escalade, Escalade ESV, Escalade EXT
	2007-2013 Chevrolet Avalanche, Silverado 1500
	2007-2014 Chevrolet Suburban, Tahoe
	2010-2015 Chevrolet Camaro
	2009-2015 Chevrolet Traverse
	2007-2015 GMC Acadia
	2007-2013 GMC Sierra 1500
	2007-2014 GMC Yukon, Yukon XL, Yukon Denali, Yukon Denali XL
	2008-2009 Pontiac G8
	2007-2010 Saturn Outlook

ABS and red brake lamp is on in the IPC.

When trying to retrieve DTCs, the scan tool will not communicate with the 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 replacement of the EBCM; however, the concern may still be present after installing the new EBCM.

Recommendation/Instructions

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

1. (If Equipped with StabiliTrak RPO JL4) The Yaw and Lateral Accelerometer (Multi-Axis) Sensor or the Steering Wheel Angle Sensor supply voltage (circuit 2087 Dk Green) shorted and 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 that is being serviced. 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. On some full size utility vehicles, the circuit may be shorted under the passenger front seat at the rear camera module bracket. Repair the circuit as necessary and reroute to prevent the concern from reoccurring
2. A shorted WSS or WSS wiring. 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 communication returns. If so, repair and/or replace any wiring/connector and/or WSS issues.

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