P0604: Internal Control Module Random Access Memory (RAM) Error

P0604 means Internal Control Module Random Access Memory (RAM) Error. The engine computer's self-test has found a fault in its working memory.

CodeP0604
SystemControl module
SeverityHigh
TypeGeneric powertrain

Can I keep driving? Limit driving and diagnose promptly. Continued driving can cause damage, stalling or limp mode.

Common symptoms

  • Check engine light on
  • Possible stalling, no-start or limp mode
  • Other modules may report communication errors

Possible causes

  • Low or unstable battery voltage
  • Poor control module ground or power supply
  • Interrupted or incorrect software programming
  • Internal control module failure
  • Water damage

How to diagnose P0604

  1. Check battery condition and charging voltage first.
  2. Check control module power and ground circuits.
  3. Check for available software updates from the manufacturer.
  4. Ask whether the module was recently reprogrammed or tuned.
  5. A replacement module usually needs to be programmed to the vehicle.

What the code means, digit by digit

PPowertrain0Generic (SAE) code6Sub-system04Specific fault

Generic codes have the same definition on every OBD-II vehicle (petrol cars from model year 1996 in the US, 2001 in the EU; diesels later). Manufacturers can add their own enhanced codes; those are not listed here.

Related codes

General guidance only. Fault codes describe what the engine computer saw, not which part failed: confirm with testing before replacing parts, and follow the vehicle's service information.