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.
DTC U0402: Invalid Data Received From TCM: Action
This DTC sets if the transmission output speed signal message from the TCM (diesel engine vehicles) or the PCM (gasoline engine vehicles) is missing. For diesel engine vehicles, RETRIEVE and DIAGNOSE all TCM DTCs. REFER to the appropriate Automatic Transmission article. For gasoline engine vehicles, RETRIEVE and DIAGNOSE all PCM DTCs. REFER to the appropriate Electronic Engine Controls article. If the diagnostic scan tool cannot communicate with the TCM or PCM, REFER to the Module Communications Network article to diagnose the no communication concern. If there are no DTCs in either module; SET the ignition to OFF, DISCONNECT and INSPECT all TCM or PCM electrical connectors for corrosion, bent pins, pushed-out pins and spread terminals. REPAIR as necessary.
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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.