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.
How the engine computer detects it
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.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- Possibly starting problems
- Transmission limp mode if the transmission module is affected
- Reduced power (GM Europe assignment)
Common causes
- Program memory corrupted by an interrupted reflash Most likely
- Internal flash or ROM defect Possible
- Faulty module software (update available) Possible
- Low voltage, voltage dips or a poor ground or supply at the module Less likely
How to diagnose P0605
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: engine control module, control module power supply, control module ground.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0605 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Hyundai Sonata | 2011–2016 | 4 | 120k |
Counts of owner complaints to the NHTSA that mention P0605 (9 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 6
- Computer and output circuits
- 05
- Specific fault
Questions drivers ask
Can I drive with code P0605?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0605?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Often reported together
Codes that owners mention in the same NHTSA complaints as P0605. They can point to a shared cause, so it's worth checking them together.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.