P0604 on Honda Civic FC: Internal Control Module Random Access Memory (RAM) Error

Short answer: P0604 means “Internal Control Module Random Access Memory (RAM) Error”. The car’s computer has found a fault in the ECM system and turns on the Check engine light (MIL). First check: check all battery and ECM power and earth connections first.

Standard OBD-II code Same meaning on all cars (SAE J2012). Not checked against this car’s factory manual.

Code

P0604

System

ECM

Dashboard light

Check engine light (MIL)

Applies to

Generic OBD-II meaning. Not every code is used by this car.

Confidence

medium (generic OBD-II definition, not checked against the factory manual for this car)

Source

obd-codes.com

Symptoms and when it is set

1. Check engine light on

Likely causes

1. Possible causes for this code include
2. PCM programming error
3. New or incorrect PCM
4. Aftermarket (high-performance) PCM program installed
5. Blown ECM/PCM fuse
6. Low battery voltage or complete battery discharge
7. Bad ECM/PCM power supply relay

What to check, in order

1. Check all battery and ECM power and earth connections first
2. Read every stored code; an ECM fault is rare, wiring faults are common
3. Have a specialist confirm before replacing the ECM

Related on this car

• All fault codes for this car
• Warning lights
• Where the parts are (parts map)
• Common problems

Same code on other cars

• P0604 · Toyota Passo (1st gen)
• P0604 · Toyota Corolla (11th gen, E170)
• P0604 · Toyota Corolla (10th gen, E140)
• P0604 · Honda City (5th gen, GM2)
• P0604 · Suzuki Wagon R (Pakistan, K10B)
• P0604 on all cars compared

← P0600 P0606 →

Clearing the code does not fix the fault. If it comes back, the problem is still there. For brakes, airbags and steering, see a trained mechanic.