What P0605 means
Internal Control Module Read Only Memory (ROM) Error
How to diagnose
- Read freeze frame data. When P0605 set, your ECU snapshotted every sensor at that moment. This tells you what the car was doing when the fault triggered — RPM, load, coolant temp, throttle position, fuel trims. Almost always enough info to figure out the cause without further testing.
- Check for related codes. If you have P0605 plus other codes, fix the earliest one in the chain first — a single root cause often triggers multiple codes.
- Cheap fixes first. For most codes, the order is: inspect connectors + wiring (free), check for vacuum leaks (cheap), replace sensor (moderate), replace mechanical part (expensive). Follow that ladder before dropping money on parts.
Manufacturer-specific descriptions
Different manufacturers use P0605 for slightly different failure modes:
| AUDI | Lack of proper voltage and or ground to the PCM, Defective PCM ROM memory module, Defective PCM ground circuit(s), Defective PCM controlled output devices |
| BMW | Internal Control Module Read Only Memory (ROM) Error |
| FORD | Powertrain Control Module ROM Test Error |
| MITSUBISHI | Internal Control Module ROM Error (Module Identification Defined by SAE J1979); ECU CPU malfunction flash ROM |
| NISSAN | Internal Control Module ROM Error (Module Identification Defined by SAE J1979) |
| VOLKSWAGEN | Control Module Programming Read Only Memory (ROM) |
Read P0605 on your own car
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