P0605Internal Control Module Read Only Memory (ROM) Error
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0605 reports an error in the module's program memory (ROM, today flash), found by a checksum or error-correction check at start-up or in the background. Ford is the main user: its engine and transmission modules compare a ROM checksum and set P0605 with the check engine light; the diesel transmission module tests once per trip at start. GM's engine module does not use P0605 and reports the same fault as P0601; the GM gateway (2025) uses it for uncorrectable ROM bit errors with two-trip logic, and GM Europe's 1.6 L engine even assigns it to processor faults of the throttle control. Which of P0601 and P0605 appears is therefore the manufacturer's choice. The usual repair is reprogramming, which restores the memory contents; replace the module only if the code returns.
- What you may notice
- Check engine light on
- Possibly starting problems
- Transmission limp mode if the transmission module is affected
- Reduced power (GM Europe assignment)
- Likely causes
- LikelyProgram memory corrupted by an interrupted reflash
- PossibleInternal flash or ROM defect
- PossibleFaulty module software (update available)
- RareLow voltage, voltage dips or a poor ground or supply at the module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.