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Service bulletin PIT-4056

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

The communication, as NHTSA indexes it (as of 2026-10-19)
TypeService bulletin
NHTSA id10022691
Published by NHTSA2007-09-20
Manufacturer's numberPIT-4056
Manufacturer's date2012-02-01
ReplacesPIT-4056G
NHTSA componentSERVICE BRAKES, AIR:ANTILOCK:CONTROL UNIT/MODULE; SERVICE BRAKES, HYDRAULIC:ANTILOCK/TRACTION CONTROL/ELECTRONIC LIMITED SLIP:CONTROL UNIT/MODULE

NHTSA's summary

GMC: UNABLE TO COMMUNICATE WITH THE EBCM DTC U0121. *NJ VEHICLES EQUIPPED WITH JL4. UPDATED 9/30/08. *PE UPDATED 6/27/11. *PE UPDATED 4/6/12. *PE

The document

No address for NHTSA's copy can be built for this communication. Ask the dealer for it by the manufacturer's number.

Components

Brakes, Anti-lock brakes

Trouble codes named

U0121

Vehicles listed
CADILLAC ESCALADE2007, 2008
CADILLAC ESCALADE ESV2008, 2009 (the catalog's model; the bulletin names a series or trim of it)
CADILLAC ESCALADE EXT2008, 2009 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET AVALANCHE2007, 2008, 2009
CHEVROLET AVALANCHE 15002007, 2008 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET AVALANCHE 15002011 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET AVALANCHE 25002007 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET CAMARO2010, 2011
CHEVROLET SILVERADO2007
CHEVROLET SILVERADO2009
CHEVROLET SILVERADO 15002007, 2008 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET SILVERADO 25002007, 2008 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET SILVERADO 35002007, 2008 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET SUBURBAN2009
CHEVROLET SUBURBAN 15002007, 2008 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET SUBURBAN 25002008 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET TAHOE2007, 2008, 2009
CHEVROLET TRAVERSE2009, 2010, 2011
GMC SIERRA2008
GMC SIERRA 15002007, 2008 (the catalog's model; the bulletin names a series or trim of it)
GMC SIERRA 25002007, 2008 (the catalog's model; the bulletin names a series or trim of it)
GMC SIERRA 35002007, 2008 (the catalog's model; the bulletin names a series or trim of it)
GMC YUKON2007, 2008

Listing a model year does not mean every vehicle of it is concerned: the document says which.

Other bulletins for the same vehicles and component
PIT3271J2019-12-09. Service bulletin. This Preliminary Information communication provides information to the technician about changing the tire and wheel size on vehicles. General Motors will only support a tire calibration for tires that have been sized, tested and designed for the vehicle in question and its applications. Technician should not use the information that is provided by the antilock braking system tire size selection.
PIT4225F2017-08-15. Service bulletin. This Preliminary Information communication provides information to the technician about vehicles that have an Antilock Braking System lamp followed by a Service Stability message in the Drivers Information Center. Technician my find Diagnostic Trouble Code C0710 set in the Electronic Brake Control Module. Technician may or may not find Diagnostic Trouble Code C0455. Technician will need to ensure the steering wheel is properly installed to the steering shaft.
PIC5432D2017-08-15. Service bulletin. This Preliminary Information communication provides information to the technician about vehicles that have an intermittent Service Stabilitrak message being displayed in the Driver Information Center only at startup and that the message is gone within seconds of starting the engine. On model year vehicles 2010 through 2012 technician will reprogram the Electronic Brake Control Module with the latest calibrations in Tis2Web.
PIC5428F2017-08-15. Service bulletin. This Preliminary Information communication provides information to the technician on how to diagnose and repair vehicles that may have the Antilock Braking System, Service Traction Control System, and/or Service Stabilitrak lights are on. The Electronic Brake Control Module may have one or more of the following Diagnostic Trouble Codes C0035-C0050 with specifically symptom 18, 5A, or 0F. Technician will gain access to the correct wheel bear per the Diagnostic Trouble Code that is set. If debris is found on the magnetic encoder ring it will needed to be cleaned.
PIC5428G2016-09-23. Service bulletin. THIS PRELIMINARY INFORMATION COMMUNICATION PROVIDES INFORMATION TO THE TECHNICIAN ON HOW TO DIAGNOSE AND REPAIR VEHICLES THAT MAY HAVE THE ANTILOCK BRAKING SYSTEM, SERVICE TRACTION CONTROL SYSTEM, AND/OR SERVICE STABILITRAK LIGHTS ARE ON. THE ELECTRONIC BRAKE CONTROL MODULE MAY HAVE ONE OR MORE OF THE FOLLOWING DIAGNOSTIC TROUBLE CODES C0035-C0050 WITH SPECIFICALLY SYMPTOM 18, 5A, OR 0F. TECHNICIAN WILL GAIN ACCESS TO THE CORRECT WHEEL BEAR PER THE DIAGNOSTIC TROUBLE CODE THAT IS SET. IF DEBRIS IS FOUND ON THE MAGNETIC ENCODER RING IT WILL NEEDED TO BE CLEANED.
PIC-5515C2013-05-08. Service bulletin. GM: SOME VEHICLES MAY EXHIBIT A RATCHET, GRIND, OR ABS PUMP MOTOR NOISES AT THE FRONT OF THE VEHICLE. *JS
PIC-5551-A2012-02-08. Service bulletin. CHEVROLET: SOME MODEL YEAR VEHICLES ARE EXPERIENCING A DROP/SPIKE IN SPEED ON ANY WHEEL SPEED SENSOR AFTER NOISE, RATCHET, GRIND, OR ABS PUMP MOTOR, WAS HEARD, FROM FRONT OF VEHICLE. *PE
PIP-49662011-12-06. Service bulletin. CHEVROLET/CADILLAC/GMC: CERTAIN VEHICLES EXPERIENCING ERRATIC OR INOPERATIVE SPEEDOMETER OR ANTI-LOCK BRAKE SYSTEM MESSAGE OR MALFUNCTIONING INDICATOR LIGHT DISPLAYING IN DRIVER'S INFORMATION CENTER. *PE UPDATED 08/5/2013 *JS
PIC-54282011-06-15. Service bulletin. GM: THE BRAKE, TRACTION, OR STABILITY LIGHTS ARE ON BECAUSE OF DEBRIS STUCK ON THE WHEEL SPEED SENSOR. UPDATED ON 06/15/2011. *KB UPDATED ON 06/20/2011. *RM UPDATED 6/27/11. *PE UPDATED 10/3/11. *PE UPDATED 05/08/2013 *JS UPDATED ON 7/9/2013. *KB UPDATED 7/28/14. *PE
PI-0097A2011-03-26. Service bulletin. GMC/SATURN/BUICK/CHEVROLET: INTERMITTENT NO CRANK/NO START; SECURITY LIGHT ON; ANTILOCK BRAKE SYSTEM (ABS) WARNING LIGHT ON; STABILITRAK INDICATOR LIGHT ON/SERVICE STABILITRAK MESSAGE DISPLAYED IN DIC; INCREASED STEERING EFFORT. *PE UPDATED 3/28/11. *PE UPDATED 3/30/11. *PE