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.
Diagnostic Aids
When class 2 serial data line is shorted to ground, U1300 will be set. Go to DTC U1300: SERIAL DATA LINE SHORT TO GROUND under DIAGNOSTIC TESTS. When class 2 serial data line is shorted to voltage, U1301 will be set. Go to DTC U1301: SERIAL DATA LINE SHORT TO BATTERY under DIAGNOSTIC TESTS. Disconnecting modules and turning the ignition switch to RUN may cause DTCs to set in these modules. Check for DTCs in each module after repair.
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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.