P0605
Internal Control Module Read Only Memory (ROM) Error
ECU self-test detected a ROM/checksum failure on the program memory. The control software cannot be trusted; vehicle typically defaults to limp-home with reduced function.
- 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.
- ECU internal ROM faultCommon
- Module software outdated, reflash may resolveLess likely
- Supply voltage outside specificationLess likely
Parts involved
- ECM
P0605 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.