P0604 Code Meaning and Next Steps

First checks take 10 to 20 minutes for the first checks. No special tools are usually needed for the first checks.

Can you keep driving?

Stop driving if any of these apply

!The engine starts stalling, losing power sharply, or the warning light flashes.
!The vehicle begins to run erratically or enters limp mode while the code is active.

If the light is steady and the vehicle still drives normally: Often yes for a short time, but it should not be ignored.

What to check first

Step-by-step checks

1
Free - no tools
Check battery and charging-system health before replacing the module
2
Free - no tools
Inspect module power and ground connections for looseness or corrosion
3
Basic tool needed
Notice whether the code appeared after a jump start, low battery, or electrical repair
4
Basic tool needed
If the vehicle has several module-related codes, look for a shared supply or ground problem
5
Basic tool needed
If scan data is available, record whether the code returns immediately after clearing

If the code returns

-If voltage or ground issues are found, solve those before blaming the module.
-If the fault repeats right away with good power, the module itself is more suspect.
-If the code follows a programming event, verify the software level and calibration first.

Background

What this code means

P0604 is a generic OBD-II code for control module RAM error.

That usually means the module detected corrupted or unreliable working memory, often after voltage problems or an internal electronic failure.

Diagnosis

Common causes

Most common

Low or unstable voltage

Voltage events can corrupt working memory in the module.

Common

Module power or ground issue

The module may not be getting stable support voltage.

Common

Internal RAM failure

The module may no longer keep its working data correctly.

Possible

Software corruption

A failed update or logic issue can trigger the error.

Avoid these mistakes

What not to do

xDo not replace a control module first if there is obvious wiring, connector, or power-supply damage.
xDo not assume a module code always means the module itself is bad before checking the supporting circuit.

Parts

Parts that may need replacing

PartTypical costNotes

Battery or charging system test$0-$50Often the best first step before replacing a module.

Power or ground repair$20-$150Relevant if support voltage is weak or unstable.

Control moduleVariesConsider only after electrical and software checks are complete.

Related OBD codes

P0601

P0601 usually means the internal control module memory checksum is incorrect.

P0602

P0602 usually means the control module has been programmed incorrectly.

P0603

P0603 usually means the control module keep-alive memory has failed.

P0605

P0605 usually means the internal control module read-only memory has failed.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0604 was expanded around internal control-module RAM faults, especially voltage events, wiring support issues, and internal electronic failure.

This guide is written as a generic multi-make reference, so bulletin history, sensor locations, and repair order can still change by manufacturer and engine family.

This is generic OBD-II guidance and should not override vehicle-specific service information. Exact diagnosis and repair steps vary by make, engine family, and model year.

Last reviewed: 2026-04-10

Reference: Open reference

P0604 - P0604 Usually Means the Internal Control Module Random Access Memory Has Failed