P0604 Internal memory (RAM) fault inside the engine or powertrain control module

Control module random access memory error

P0604 in short

P0604 means the engine or powertrain computer found a fault in its own memory (RAM). Low battery voltage, a fuse or power supply problem, outdated programming or a failing module can cause it. KBB calls it serious, so have it diagnosed soon rather than driving on it.

The control module runs self-checks on its memory each time it starts. P0604 sets when the check of its random access memory fails, so the module may not be able to run the engine reliably.

KBB lists fuse issues, loose battery terminals, power supply wiring faults, low battery voltage, programming and, rarely, a defective module. Symptoms range from only a check engine light to a no-start.

GM bulletins show it is not always a dead module: PIP-4653 B says the code can be stored in the transmission module and set in the engine module too, so confirm which one set it. GM also lists P0603 and P0604 as the cause of the SES light on 2007-2008 Sky and Solstice, and Toyota has a 2003-2004 Camry and Solara bulletin with P0604.

Most likely causes

  1. Low battery voltage, loose terminals or a power supply fault to the module

    Common general cause
    Why it ranks here
    KBB lists low battery voltage, loose terminals, fuse issues and power wiring faults ahead of a module failure.
    What would change this
    Rises if the battery is weak or voltage dips, or a fuse or ground is bad. Falls if supply and grounds test good.

  2. Module programming or software

    Common general cause
    Why it ranks here
    KBB lists programming problems; a Cobalt owner reports a dealer reprogramming and relearning after P0604 and P0606.
    What would change this
    Rises if updated programming is available for your VIN. Falls if software is current and the code returns.
    How to test the engine control module (ecm / pcm)

  3. Failed engine or powertrain control module

    Supported by vehicle data
    Why it ranks here
    GM bulletin 4198 attributes the SES light on 2007-2008 Sky and Solstice to internal ECM codes P0603 and P0604, and an owner report shows an ECM replaced for P0604.
    What would change this
    Rises if the code returns after power and software are ruled out. Falls if power is faulty or programming fixes it.
    How to test the engine control module (ecm / pcm)

  4. Code stored in a different module than the engine module

    Supported by vehicle data
    Why it ranks here
    GM PIP-4653 B says P0604 can be stored in the transmission module and also set in the engine module, so confirm which module set it.
    What would change this
    Rises if the scan tool shows the code in another module. Falls if it is only in the engine module.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Scan all modules, not only the engine module, and note which one stored P0604 and any other module or voltage codes.

    Low riskTool: OBD-II scan tool that reads all modules

  2. Have the battery, terminals, fuses, grounds and charging voltage tested.

    Low riskTool: battery tester, multimeter

  3. Ask a dealer to check for updated module programming for your VIN and to repeat the memory check.

    Best left to a shopTool: dealer scan tool

    Warning:This needs specialist tools and vehicle service information. Leave it to a shop.

Symptoms

  • Check engine light on
  • Engine stalls Gets more serious: stop and have it checked.
  • Engine will not start Gets more serious: stop and have it checked.
  • Poor drivability or shifting

How to fix

  1. Have the battery and its terminals checked.

Parts and cost context

  • Engine control module (ECM / PCM):The module is the last suspect and may need programming to the vehicle. Rule out power, grounds and software first; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Saturn

  • 2007–2008 · Sky

    Supported by vehicle data

    GM bulletin 4198 ties an SES light to internal ECM codes P0603 and P0604. Whether the bulletin is still current is not verified.

  • 4198Status unverified

    SES light with ECM codes P0603 or P0604

    2007–2008sky · NHTSA 10022797

    The SES light may come on due to internal ECM codes P0603 and/or P0604.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Toyota

  • 2003–2004 · Camry

    Supported by vehicle data

    Toyota bulletin 05104 lists MIL on with P0604, P0606 and P0607. Whether the bulletin is still current is not verified.

  • 05104Status unverified

    MIL on with P0604, P0606 and/or P0607

    2003–2004camry, camry-solara · NHTSA 10011863

    Toyota bulletin for the malfunction indicator lamp with these codes; the summary does not state the repair.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2008–2010 · Malibu

    Supported by vehicle data

    GM PIP-4653 B says P0604 can be stored in the transmission module and set in the engine module. Whether the bulletin is still current is not verified.

  • PIP-4653 BStatus unverified

    P0601, P0603, P0604, P062F and P1621 stored in the transmission module

    2008–2010malibu, corvette, equinox, traverse · NHTSA 10032434

    The codes can be stored in the transmission module and set in the engine module; confirm which module set the code.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0601Control module internal memory checksum error

    Same system Possible — needs testing

    P0601 is the module memory checksum code, in the same family of internal module faults.

  • P0606A control module found a fault in its own processor or programming

    Same system Supported by vehicle data

    P0606 is the processor fault code. A Cobalt owner reports P0604 and P0606 together, and Toyota lists them together.

All Engine computer (ECM/PCM) codes

P0604 questions

Does P0604 always mean I need a new computer?

No. Low voltage, a bad fuse or ground, or outdated programming can cause it, and the code may be stored in another module on some GM vehicles.

Sources and review

  1. P0604 code page (OBD-II codes) — Kelley Blue Book
  2. GM bulletin 4198 (NHTSA 10022797): Sky and Solstice SES light with ECM codes P0603 or P0604 — General Motors
  3. NHTSA complaint ODI 10980316: Chevrolet Cobalt 2005, P0604 and P0606 control module RAM failure — NHTSA Office of Defects Investigation
  4. NHTSA complaint ODI 10470386: Buell 1125R 2009, ECM code P0604 RAM failure replaced — NHTSA Office of Defects Investigation
  5. GM PIP-4653 B (NHTSA 10032434): P0601, P0603, P0604, P062F, P1621 stored in TCM — General Motors
  6. Toyota bulletin 05104 (NHTSA 10011863): MIL on with P0604, P0606 and/or P0607 on 2003-2004 Camry and Solara — Toyota Motor Sales
Last reviewed
Written by
Saurabh K.
Editorial review
Pending
Technician review
Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

My Car

Pick your car and code pages will point out notes and bulletins for it. Saved only in this browser.

Fill this in from your VIN

Used once to identify your engine; not stored.