P0606: Control module processor fault
The engine computer has found a fault in its own processor or internal checks. The engine may lose power, run erratically or stall.
Updated
What P0606 means
The engine computer keeps checking itself while it runs: its memory, its processor and, on many cars, a second processor that watches the electronic throttle. P0606 means one of those internal checks failed.
It doesn’t always mean the computer is broken. A poor supply voltage or earth connection can upset it, and for some cars the manufacturer has a software update for it.
P0601 to P0607: the engine computer’s other self-checks
The engine computer also checks its memory and its programming. P0601 is a memory checksum error, P0602 a programming error, P0604 and P0605 errors in its working memory (RAM) and read-only memory (ROM), and P0607 a failed performance check. The same order of checks applies: the supply voltage and the earths first, then a software update, and only then a new computer.
P0603, the keep-alive memory that holds what the computer has learnt, is often milder and can follow a weak battery or a poor battery connection. It has its own driving advice, below.
P0601: Internal control module memory checksum error
The engine computer has found an error in its memory when checking it (a checksum error): its software or memory may be corrupt.
Common causes: internal fault in the engine computer, software corrupted, for example by an interrupted update, poor supply voltage or earth connection to the engine computer.
P0602: Control Module Programming Error
The engine computer reports that it isn’t programmed, or isn’t programmed correctly.
Common causes: software update or programming interrupted or incomplete, replacement engine computer not programmed for this car, internal fault in the engine computer.
P0603: Internal Control Module Keep Alive Memory (KAM) Error
The engine computer’s keep-alive memory, which holds what it has learnt about the engine while the car is switched off, failed its self-test. The engine runs on default values until it has learnt again.
Common causes: weak battery, or a loose or corroded battery or earth connection, aftermarket engine tuning device, internal fault in the engine computer.
Driving: Drive gently and have it checked soon. While the engine computer runs on default values, the engine may idle roughly, stumble or stall. If it stalls or runs badly, don’t drive on: have it checked first.
P0604: Internal Control Module Random Access Memory (RAM) Error
The engine computer has found an error in its working memory (RAM) when checking itself.
Common causes: internal fault in the engine computer, software or programming fault, poor supply voltage or earth connection to the engine computer.
P0605: Internal Control Module Read Only Memory (ROM) Error
The engine computer has found an error in its read-only memory (ROM), where its software is stored.
Common causes: internal fault in the engine computer, software corrupted, for example by an interrupted update, poor supply voltage or earth connection to the engine computer.
P0607: Control Module Performance
The engine computer’s check of its own performance failed: it has found a fault inside itself.
Common causes: internal fault in the engine computer, for example from water getting in, software fault, or an update that wasn’t done properly, poor supply voltage or earth connection to the engine computer.
Can I keep driving?
Drive gently
Drive gently and only as far as you need to, and have it checked soon. The engine can cut out without warning and may not restart; steering and braking then get much heavier. Avoid motorways and long trips until it’s fixed.
General guidance based on the code alone, not on the car’s actual condition. If in doubt, stop and ask a mechanic.
The engine computer controls the throttle, fuel and spark, so many cars go into limp mode with P0606: reduced power, or the engine held at idle.
Symptoms
- Limp mode or reduced power.
- Stalling, or the engine won’t start.
- Erratic running, often with other fault codes.
Common causes
- Internal fault in the engine computer. For example from water getting in, heat or age.
- Poor supply voltage or earth connection to the engine computer. Check this first: it’s cheaper to fix, and a new computer would suffer the same way.
- Software fault: for some cars there’s an update for it. A dealer for your make can tell you whether one exists.
Typical fixes
- Check the battery, its clamps and the earth straps, and the voltage in live data.
- Ask a dealer for your make whether there is a software update or a known fix for this code on your car.
- Have the engine computer’s power supply, earths and connectors checked.
- Have the engine computer repaired or replaced if those are fine. On most cars a replacement has to be coded to the car, including the immobiliser.
Questions
Can I drive with P0606?
Gently, and only as far as you need to: the engine can cut out without warning and may not restart, and steering and braking then get much heavier. Avoid motorways and long trips, and have it checked soon.
Does P0606 mean the engine computer must be replaced?
Not always. Check the supply voltage and earth connections first, and ask about a software update. Replace the computer only when those are ruled out.