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 P0603: Problem in Transmission Control Module (TCM): General Description
The electronically erasable programmable read-only memory (EEPROM) in the transmission control module (TCM) can read data to/from its memory. This memory also can hold data even after the battery is disconnected. If an abnormality in the data read from the EEPROM occurs a set number of times, the CPU detects a malfunction and stores a DTC.
| Execution | Once per driving cycle |
| Sequence | None |
| Duration | 60 seconds or less |
| DTC Type | One drive cycle, MIL ON, D indicator blinks |
| Condition | |
|---|---|
| Ignition switch | ON |
| Other | When disconnecting and reconnecting the battery |
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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.