P0601
Internal Control Module Memory Check Sum Error
The ECU's internal memory checksum does not match the expected value at startup — the firmware/calibration in flash has become corrupt. Often appears after a failed flash, low battery during programming, or genuine module hardware failure.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
Common causes
Ordered by how often each turns out to be the cause.
- Failed flash / interrupted programmingPossible
- Module hardware failurePossible
- Module software outdated, reflash may resolveLess likely
Parts involved
- ECM
P0601 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.