P0605 code meaning
Internal Control Module Read Only Memory (ROM) Error
Powertrain system Generic code P06xx codes Check engine light
What P0605 means
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.
P0605 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0605
- Check engine light on
- Possibly starting problems
- Transmission limp mode if the transmission module is affected
- Reduced power (GM Europe assignment)
Common causes of P0605
- Most likelyProgram memory corrupted by an interrupted reflash
- PossibleInternal flash or ROM defect
- PossibleFaulty module software (update available)
- Less likelyLow voltage, voltage dips or a poor ground or supply at the module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Engine control moduleControl module power supplyControl module ground
What each part of P0605 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 05 | The exact fault in that area. |
What to do next
- Note P0605 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0605
What does P0605 mean?
P0605 means "Internal Control Module Read Only Memory (ROM) Error". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0605?
Drive gently and only to a workshop. With P0605 the car can go into limp mode (reduced power) to protect itself.
Will P0605 fail an emissions test?
Yes, it can. P0605 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0605 to fix?
Difficulty: hard. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P0605 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.