P0604
Internal Control Module Random Access Memory (RAM) Error
ECM / control module
Generic OBD-II
High
What it means
P0604 means the engine control module has detected an internal error in its own RAM (working memory). Because the ECM manages fuel, ignition, and more, this can cause reduced power, stalling, or a no-start. It is often triggered by a weak battery or poor power/ground connections rather than a truly dead module, so those are worth checking before condemning the ECM.
High
Can I keep driving? Drive cautiously — an internal module fault can trigger limp mode, stalling, or even a no-start, so get it diagnosed before relying on the car.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced power or limp mode
- Stalling or rough running
- Hard starting or, in some cases, a no-start
Common causes
Most likely first
- Low battery voltage or a weak/failing battery upsetting the moduleLikely
- Poor power or ground connections at the ECMCommon
- Corrosion or moisture in the ECM connectorsCommon
- Internal ECM RAM fault (the module itself failing)Less often
- Interrupted or corrupted software after a battery disconnect or bad flashLess often
How to diagnose & fix
Work through it in order
- Test the battery and charging system; a weak battery is a common trigger for internal-memory codes.
- Inspect and clean the ECM power and ground connections and connectors.
- Clear the code and see if it returns after a few drive cycles.
- Check for a manufacturer reflash/software update for the ECM.
- If the fault persists with good power and grounds, the ECM likely needs reprogramming or replacement.
FAQ
Quick answers
Is it safe to drive with P0604?+
Be careful. The module reporting an internal memory error can cause unpredictable running, stalling, or a no-start. Have it diagnosed before depending on the vehicle.
Can I just clear P0604?+
It may clear temporarily, but if the battery/grounds are bad or the module is failing it returns. Fix the power supply first, then reassess the ECM.
Related codes
Often seen with P0604
Read & clear P0604 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX