P0606
ECM/PCM Processor Fault
The ECU's internal processor self-test has failed. This is a hard module fault — the ECU usually triggers limp-home mode and may not respond to scan tools fully until replaced or repaired.
- 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.
- Internal processor or memory failureCommon
- Water ingress / corrosion in moduleLess likely
- Module software outdated, reflash may resolveLess likely
Parts involved
- ECM
P0606 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.