OBD-II diagnostic trouble code
P0603Caution

Internal Control Module Keep Alive Memory Error

The section of ECU memory that stays powered even with the ignition off (holding learned values like idle and fuel trim) has a fault, similar in cause to the checksum error code.

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Code names are compiled from open/standardized SAE and ISO references. Explanations, symptoms, causes and fixes are original. Covers generic (P0/C0/B0/U0) codes only — manufacturer-specific codes are planned for a future update.

Frequently asked questions

Can I drive with P0603?

You can usually keep driving with P0603, but don't put it off — the underlying cause can get worse or lead to further damage the longer it goes unaddressed. Get it diagnosed as soon as you reasonably can.

How much does it cost to fix P0603?

The cost varies too much by cause and vehicle to give a single figure here — a diagnosis will narrow it down.

What causes P0603?

AS
Reviewed by Artyom SemenovAutomotive Editor · Fact-checked by Yauheni Kapliarchuk, Editor-in-Chief
Code names compiled from open SAE/ISO references; explanations and repair guidance are original editorial content
Last verified: 09 Jul 2026 · Our methodology