P0605: Internal Control Module Read Only Memory (ROM) Error
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Same caution as P0601 - the computer distrusts its own read-only memory.
Symptoms
- Persistent code returning after clear
- Limp mode or erratic behavior possible
Likely causes, most common first
- ROM checksum failure inside the PCM
- Voltage spikes damaging memory
- Module aging
Read P0605 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0605 targets the computer's read-only memory specifically. The diagnostic tree is short: verify clean power and grounds, attempt a reflash, and if the checksum fails again, the silicon is done.
Before any module replacement, insist the shop verifies supply circuits - a corroded ground imitates every internal PCM code in the book and costs fifty dollars to fix instead of fifteen hundred.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P0605
“Purchased car with just under 97000 miles. Was working terrific. Time for the first oil change and 2 miles after the change the car froze and went limp. Traveling 45 miles per hour it recorded a trouble code on my monitoring device. P0605 - ROM error and the car was dead. All lights had lit up on the panel and then it was off. Luckily was able to recover to the side and turn into a parking lot. Oil was low the night before and refiled before oil change. An additional code was recorded on Feb 12 P0128 Coolant Thermostat Malfunction. The selling dealer cleared the code and said the car was fine. I think there may be an additional issue here and why the oil was low.”2016 Hyundai Sonata · Mar 2023
“While driving at high speeds car jerks and removes itself from cruise control and rpm gauge drops to zero and stays there (has occurred without cruise control being on as well). When the car slows down to 30 mph or less, or while sitting at a red light, it shakes violently. Has occurred multiple times w/o personal mechanic being able to diagnose problem. One time, the check engine light came on and error code p0605 was identified. Battery was changed and check engine light went away, however, the violent jerking occurred later that same day exhibiting all the same issues as previous occurrences.”2013 Hyundai Tucson · Aug 2019 · 144,000 mi
Cars that report P0605 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0605?
Same caution as P0601 - the computer distrusts its own read-only memory.
How much does it cost to fix P0605?
Typical US repair costs range from $100 for the simplest fix (reflash attempt) to $2,000 in the worst case. The right number depends on which cause your car has - see the causes list.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.