service trailer brakes
- Thread starter bigred93
- Start date
There are codes in the system for it. Might to find someone with a nice snap on scanner or a tech2 to access the chassis side of the truck.
Generally the most common issue on the service brakes soon is that the cover gets broke off the back of the plug connector. Then you go and wash your truck and the water fills up inside and it shorts the plug. Which in return CAN blow fuses. If your covers broke off, you can look inside and see if its burned up inside. If it is, unplug it from main harness, replace fuses and see if it goes away. But with all the lights you have on i doubt its gonna be your issue
Generally the most common issue on the service brakes soon is that the cover gets broke off the back of the plug connector. Then you go and wash your truck and the water fills up inside and it shorts the plug. Which in return CAN blow fuses. If your covers broke off, you can look inside and see if its burned up inside. If it is, unplug it from main harness, replace fuses and see if it goes away. But with all the lights you have on i doubt its gonna be your issue
Didn't by chance just reprogram tire size for oversize tires did you?
Sent from my SAMSUNG-SM-G870A using Tapatalk
Sent from my SAMSUNG-SM-G870A using Tapatalk
I would climb under the truck and check the harness from trailer plug all the way forward. It may be possible you have chaffed wires or damage from road debris kickup.
This is off of GMs bulletins. Doesnt list it for HD trucks but can be a start somewhere. Id need to know the vin number and look at certain build codes for it to get deeper into it. Post vin if you want
Service Information Home Publications Number Search New Bulletins Bulletin Search Feedback Help
2009 Chevrolet Silverado - 4WD | Cheyenne, Sierra, Silverado VIN C/K Service Manual | Document ID: 2759190
#PIT4056G: Unable To Communicate With The EBCM DTC U0121 - (Jan 27, 2012)
Subject: Unable To Communicate With The EBCM DTC U0121
Models: 2008 - 2012 Buick Enclave
2007 - 2012 Cadillac Escalade, Escalade ESV, Escalade EXT
2007 - 2012 Chevrolet Avalanche, Silverado LD, Suburban, Tahoe
2010 - 2012 Chevrolet Camaro
2009 - 2012 Chevrolet Traverse
2007 - 2012 GMC Acadia, Sierra LD, Yukon, Yukon XL, Yukon Denali, Yukon Denali XL
2008 - 2009 Pontiac G8
2007 - 2010 Saturn Outlook
Equipped with RPO JL4
This PI was superseded to update recommended field along with model and model years. Please discard PIT4056F.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some owners may comment that the 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 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.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
© 2015 General Motors. All rights reserved.
Service Information Home Publications Number Search New Bulletins Bulletin Search Feedback Help
2009 Chevrolet Silverado - 4WD | Cheyenne, Sierra, Silverado VIN C/K Service Manual | Document ID: 2759190
#PIT4056G: Unable To Communicate With The EBCM DTC U0121 - (Jan 27, 2012)
Subject: Unable To Communicate With The EBCM DTC U0121
Models: 2008 - 2012 Buick Enclave
2007 - 2012 Cadillac Escalade, Escalade ESV, Escalade EXT
2007 - 2012 Chevrolet Avalanche, Silverado LD, Suburban, Tahoe
2010 - 2012 Chevrolet Camaro
2009 - 2012 Chevrolet Traverse
2007 - 2012 GMC Acadia, Sierra LD, Yukon, Yukon XL, Yukon Denali, Yukon Denali XL
2008 - 2009 Pontiac G8
2007 - 2010 Saturn Outlook
Equipped with RPO JL4
This PI was superseded to update recommended field along with model and model years. Please discard PIT4056F.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some owners may comment that the 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 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.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION
© 2015 General Motors. All rights reserved.
I had the service trailer brake system message and it ended up being a corroded wire above my spare tire.