P0603 means Internal Control Module Keep Alive Memory (KAM) Error. The engine computer has lost or found an error in its keep-alive memory, the memory that stores learned values such as fuel trims and idle settings while the vehicle is off. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0603 means
Modern vehicles have many control modules that share information over a network, usually called the CAN bus. Codes starting with U mean a module has stopped hearing another one, and voltage and processor codes mean a module is not getting clean power or has an internal fault. Low battery voltage, poor grounds, blown fuses and damaged wiring cause many of these codes, so test the battery and charging system first.
P0603 symptoms
- Check engine light
- Possible stalling, no start or erratic running
- Other warning lights on some vehicles
Common causes of P0603
- Low or unstable battery voltage, or a recent jump-start
- Poor power or ground to the module
- Internal module fault
- Interrupted programming or update
How to diagnose P0603
- Check battery and charging voltage
- Check module power and ground circuits
- Clear the code and see whether it returns
- Check for software updates for the module
Can you drive with P0603?
It depends on the symptoms; if the engine runs normally, drive carefully to a shop, but stalling or no-start needs attention first.
P0603 tips
KAM codes often set after the battery was disconnected or very low. Clear the code and drive; if it does not return, no repair may be needed.
Will P0603 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0603 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0606 | Control Module Processor |
| P0601 | Internal Control Module Memory Check Sum Error |
| P0562 | System Voltage Low |
Guides that help
When it is more than a sensor
Voltage and network codes come from wiring, the battery, the charging system or a module, not from engine or transmission wear. If a lost-communication code has left the transmission in limp mode, rule out the module and wiring before deciding the unit has failed, and see our transmissions only if testing confirms internal damage.
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