P0604Internal Control Module Random Access Memory (RAM) Error
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0604 means the module's working memory (RAM) failed its self-test: a value written to a cell does not read back correctly, a built-in hardware test fails, error correction reports faults, or protected memory is written without permission. GM's engine module scans the whole RAM within 30 s of start-up and then keeps checking in the background, setting the code after repeated failures with the lamp in the first trip; Ford tests RAM during initialisation, the GM gateway with error correction at start (two trips). Unlike most memory codes, P0604 is used the same way by GM, Ford, Chrysler and Saab. Consequences depend on the module: a transmission module goes into limp mode with maximum line pressure and a fixed gear, an engine module may reduce power. The code alone does not say which module set it – the scan tool shows whether it is the engine, transmission, brake or body module.
- What you may notice
- Check engine light on
- Limp mode or transmission limp mode
- Intermittent stalling or starting problems
- Several module codes at the same time
- Likely causes
- LikelyInternal hardware defect of the module (RAM)
- PossibleLow voltage, voltage dips or a poor ground or supply at the module
- RareFaulty module software (update available)
- RareMoisture or corrosion in the module or at its connector
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.