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.
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HOMESERVICE MANUALSCADILLAC2013ATS 2.0L ENG VIN X, AWDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISDATA COMMUNICATION SYSTEMDIAGNOSTIC INFORMATION AND PROCEDURESDTC U0028: MOST BUSCIRCUIT/SYSTEM VERIFICATION
2013 Cadillac ATS 2.0L Eng VIN X, AWD
Circuit/System Verification
2013 Cadillac ATS 2.0L Eng VIN X, AWDSECTION Circuit/System Verification
- Ignition ON. Radio ON.
- Verify DTC U0100-U02FF is set.
- If the DTC is set
Refer to DTC U0100-U02FF .
- If the DTC is not set
- If the DTC is set
- Verify DTC U2098 or DTC U0029 02 is set.
- If any of the DTCs are set
Refer to DTC U2098 .
- If none of the DTCs are set
- If any of the DTCs are set
- Verify DTC U0028 is set.
- If the DTC is set as a current DTC
- Access the A11 Radio's Last Working MOST ID of Node 1-9 parameters with a scan tool to view MOST device location IDs and MOST bus configuration.
- Access the A11 Radio's Surrogate MOST Master Node Upstream Position parameter with a scan tool to determine the surrogate MOST Master device and where the MOST ring break occurs. For more information, refer to Diagnostic Aids section.
- Refer to Circuit/System Testing.
- If the DTC U0028 is set as a history DTC along with other DTCs set
Diagnose all other DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- If the DTC U0028 is set as a history DTC with audio or display malfunction and without other DTCs set
- Access the A11 Radio scan tool data display to record the value of the Surrogate MOST Master Node Upstream Position and the Number of MOST Communication Breaks parameters.
- Refer to Diagnostic Aids section to help determine the MOST bus configuration, the surrogate MOST Master device and where the MOST ring break occurs to assist in the isolation of intermittent condition.
- Refer to Circuit/System Testing.
- If the DTC U0028 is not set
- Refer to Repair Verification.
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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.