Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit/System Verification
- Determine the device that is not communicating. Refer to Control Module U Code List .
- Verify that DTC U0073, U2100, U0074, U0078, U1814, U2099, B1325, B1330, B1370, B1380, B1424, B1440, B1441, B1517, C0800, C0899, C12E1, P0560 or P0562 is not set.
- If any of the DTCs are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- If none of the DTCs are set
- If any of the DTCs are set
- Verify that DTC U0125 and DTC U0126 are not set together.
- If both of the DTCs are set together
Refer to Scan Tool Does Not Communicate with Chassis High Speed GMLAN Device .
- If both of the DTCs are not set together
- If both of the DTCs are set together
- Engine running for 10 s.
- Ignition ON, engine OFF, verify that DTC U0100-U02FF is not set.
- If the DTC U0100-U02FF is set in any device, except the K17 Electronic Brake Control Module
Refer to Circuit/System Testing.
- If the DTC U0100-U02FF is set in the K17 Electronic Brake Control Module with any symptom byte, except symptom bytes 71, 72 and 74
Refer to Circuit/System Testing.
- If the DTC U0100-U02FF is set in the K17 Electronic Brake Control Module with symptom byte 71, 72 or 74 along with other DTCs set
Diagnose all other DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- If the DTC U0100-U02FF is set in the K17 Electronic Brake Control Module with symptom byte 71, 72 or 74 and without other DTCs set
- Program the K17 Electronic Brake Control Module.
- Verify the DTC does not set.
- If the DTC sets, replace the K17 Electronic Brake Control Module.
- If the DTC does not set
- All OK.
- If the DTC U0100-U02FF is not set
- If the DTC U0100-U02FF is set in any device, except the K17 Electronic Brake Control Module
- All OK.
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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