P0604 Internal control module random access memory (RAM) error
What P0604 means
The engine control unit tests its working memory and has found an error. The processor may not be able to calculate correctly, so engine behaviour can become unpredictable.
P0604 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Typical repair cost
- 400–2000 €
- Workshop time
- 1–4 h
- Repair difficulty
- Hard
- DIY possible
- No
- Check engine light
- Yes
- Affects emissions test
- No
- Limp mode possible
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine light on
- Stalling or no start
- Erratic running or limp mode
- Several warning lights
Common causes
- Internal failure of the engine control unit
- Unstable supply voltage or poor ground
- Water or corrosion inside the control unit
- Damage from a voltage spike
Can I keep driving with P0604?
Stop as soon as it is safe and have it checked. A working-memory fault can cause unpredictable engine behaviour or a complete shutdown while driving.
What to check first
- Check the battery, charging voltage and ECU grounds
- Inspect the control unit and connectors for water or corrosion
- Clear the code and see if it returns immediately
- Have the control unit repaired or replaced and programmed
Related codes
- P0603 Internal control module keep alive memory (KAM) error
- P0605 Internal control module read only memory (ROM) error
- P0602 Control module programming error
- P0606 Control module processor fault
- P0601 Internal control module memory checksum error
- P0607 Control module performance
- P0600 Serial communication link
- P0610 Control module vehicle options error
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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