P0603: Internal control module keep alive memory (KAM) error
The ECU has lost the data it keeps with the ignition off. Almost always a disconnected or flat battery or a power supply fault.
| Code | P0603 |
|---|---|
| System | Engine and transmission |
| Group | P06xx, Control unit and auxiliary outputs |
| Type | Generic: it means the same on every make |
| Can you keep driving? | Yes, no rush |
What P0603 means
The ECU stores what it learns about the engine, such as fuel trim and idle settings, in a special memory called KAM, even with the key out. To do that it needs a permanent feed from the battery. If that memory is wiped or fails, this code appears.
Most common causes
- Battery recently disconnected or replaced
- Battery very flat or terminals making poor contact
- ECU permanent supply fuse blown or loose
- ECU supply or earth wire in poor condition
- Internal ECU fault
Symptoms
- Engine warning light on
- Unsteady idle for the first few miles
- Engine may run slightly worse until it relearns
Can you drive with P0603?
Yes, no rush You can normally drive without any problem. If the code keeps returning without the battery being touched, get it checked.
How to check it
If you have disconnected or replaced the battery, clear the code and drive normally for a few days. If it returns, check the terminals and the ECU permanent supply fuse, and look at the voltage with the engine off.
How to read and clear P0603 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0603 with this same explanation and whether it’s confirmed, pending or permanent.
With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.
Similar codes
- P0600 Serial communication link fault
- P0601 Internal control module memory checksum error
- P0602 Control module programming error
- P0604 Internal control module random access memory (RAM) error
- P0605 Internal control module read only memory (ROM) error
- P0606 ECM/PCM processor fault
- P0607 Control module performance
- P0615 Starter relay: circuit fault
- P0616 Starter relay: circuit low
- P0617 Starter relay: circuit high
- P0620 Generator control: circuit fault
P0603 is a generic code, so it means the same on any make, for example on Citroën, Ford, Hyundai, Mercedes-Benz, Renault, Volvo. See what Final OBD does on your car in makes and models.
What does code P0603 mean?
The ECU stores what it learns about the engine, such as fuel trim and idle settings, in a special memory called KAM, even with the key out. To do that it needs a permanent feed from the battery. If that memory is wiped or fails, this code appears.
Can you drive with P0603?
You can normally drive without any problem. If the code keeps returning without the battery being touched, get it checked.
How do you clear P0603?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0603 comes back.
Read it on your car
Final OBD reads the faults of every control unit for free, including each make’s own codes, and with Pro explains each one in plain English. Free clears engine faults at no cost.
Coming soon
Mid to late October 2026
If you want to try it in your car before anyone else, send us your email and we will add you as a tester.
info@finalobd.com