Computer & output circuits · Powertrain · generic (SAE-defined)
P0605: Internal Control Module Read Only Memory (ROM) Error
P0605 means the engine computer detected an error in its read only memory (ROM), where its operating program and calibration are stored.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0605 sets
The powertrain control module (PCM) verifies its read only or flash memory during self-tests, often by comparing a calculated checksum against a stored value. When the stored program fails this check, the PCM sets P0605. The exact self-test is manufacturer-specific; definitions can vary by manufacturer, so check factory service information.
Common causes of P0605
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Corrupted PCM software or interrupted reprogramming
- Internal PCM memory failure
- Low voltage or voltage spike damaging the module
- Poor PCM power or ground connections
- Moisture or corrosion inside the PCM
P0605 symptoms
- Check engine light on
- Reduced power or limp mode on some vehicles
- Stalling or no-start
- Electronic throttle warning light on some models
How P0605 is diagnosed
- Record freeze frame data and all codes, including throttle-control codes
- Check for service bulletins and available software updates for the PCM
- Verify battery, charging voltage and PCM power and ground circuits
- Clear the code and confirm whether it returns on the next key cycle
- Reflash the PCM with the correct calibration
- Replace and program the PCM if the code returns after a successful reflash
Typical fixes for P0605
- Reprogram the PCM with the latest calibration
- Repair PCM power or ground circuit faults
- Replace the PCM and program it to the vehicle
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Manufacturer notes
Definitions can vary by manufacturer; check factory service information and software bulletins before replacing the module.
Related codes & warning lights
P0605 FAQ
What does code P0605 mean?
P0605 means the engine computer detected an error in its read only memory (ROM), where its operating program and calibration are stored. The standard definition is "Internal Control Module Read Only Memory (ROM) Error."
Can I drive with a P0605 code?
It is best to drive as little as possible. Some vehicles run normally with this code while others stall, refuse to start or go into reduced power, so get it diagnosed promptly.
Why would a ROM error affect the throttle?
On vehicles with electronic throttle control, the PCM disables or limits the throttle when it cannot trust its own program. That protective strategy is what causes reduced power.
Do I need a dealer to fix P0605?
Not necessarily, but the repair often needs factory-level programming software and the correct calibration file, which many independent shops have access to.
Keep researching
More computer & output circuits codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.