What Should You Do Right Now If Your Car Has P0604?
Stop clearing the code hoping it will stay away — it will not. Avoid long journeys in limp mode if the car will run, as this puts additional stress on drivetrain components compensating for the restricted ECU output. Get in touch with us via the contact page or call 0203 489 2610 and describe what you are seeing. We can often give you a strong initial assessment over the phone based on your vehicle, mileage and the full fault code list before you even post anything to us. There is no obligation, no hard sell — just honest advice from people who repair these units day in, day out.
Frequently Asked Questions — P0604 ECU RAM Fault
P0604 means the ECU has detected an internal RAM (Random Access Memory) error during its own self-test. The control module continuously monitors its internal memory and when a read/write failure occurs, it stores P0604 and typically restricts vehicle operation — often triggering limp mode or a no-start condition. The fault is internal to the ECU hardware and does not indicate a wiring or sensor problem.
Driving with P0604 active is not recommended. The vehicle will usually operate in limp mode, which limits engine power and in some cases maximum speed. In more severe instances the car will not start at all. Continued driving in limp mode places additional strain on the gearbox, clutch and other drivetrain components that are working harder to compensate. Get the ECU assessed as soon as practical.
No. Clearing P0604 with a scan tool will switch off the warning light temporarily, but the underlying RAM fault inside the ECU will cause the code to return almost immediately — often within a few minutes of driving. The ECU hardware must be repaired at component level for the fault to be resolved permanently. Clearing and ignoring the code risks being stranded.
A main dealer typically quotes for a brand-new replacement ECU — often between £800 and £1,800 plus VAT — before adding programming and security coding charges that can push the total considerably higher. The Vehicle Check repairs the existing unit at component level, which means most customers save 60 to 80 percent of that figure. You also retain your original unit, which is already coded to your vehicle, avoiding reprogramming costs entirely.
Call us first on 0203 489 2610 so we can log your unit and take vehicle details. Then remove the ECU from your car, wrap it in bubble wrap or foam padding, place it in a sturdy box and send it tracked to: Office 13, 25 Mollison Avenue, Enfield, EN3 7NJ. We will confirm receipt, carry out our assessment and contact you with a repair report and cost before proceeding. Full guidance is on our mail-in repair page.
The list above covers our most requested services — but it is far from everything we do. If your unit is not listed, get in touch. Our technicians have most likely seen it before and can help.
