What it means
The control module detected an error involving its read-only memory (ROM). The code alone does not establish the cause or the vehicle's operating strategy.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Read-only memory (ROM) holds the module's fixed operating program and calibration data. P0605 sets when the module's internal check detects a ROM problem, which may reflect corrupted software, a hardware fault, or supply voltage outside specification.
Common causes
Most likely first.
- ECU internal ROM fault
- Module software outdated, reflash may resolve
- Supply voltage outside specification
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
How to diagnose it
- Save freeze-frame data and scan all modules for related faults to identify whether the issue appeared alongside a voltage or communication problem.
- Check battery condition and inspect module power, ground, and connectors for poor contact or corrosion.
- Review recent repair and programming history for an interrupted flash or incorrect module installation.
- Check the manufacturer's service information for the module's correct calibration and any applicable software update.
- If P0605 returns with stable power and correct programming, test module circuits to specification and evaluate the module for an internal ROM fault.
Common fixes
- Repair poor module power, ground, or connector connections.
- Correct any battery or charging-system voltage problem.
- Reflash the module with the correct manufacturer-approved software when applicable.
- Replace and configure the module if its ROM fault is confirmed.
Can I keep driving?
If the vehicle runs normally, drive only as needed and avoid high-speed or remote trips because a ROM fault can lead to limp mode or a no-start. Do not continue if the engine stalls or control becomes unreliable.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.