P0603 - Internal Control Module Keep Alive Memory (KAM) Error

The Technical Definition: The PCM lost its continuous battery power required to keep its internal memory (emissions readiness monitors, idle relearn data, etc.) alive.

Common Symptoms: Usually, there are no drivability symptoms, but the check engine light will illuminate and the Jeep will fail an emissions plug-in test.

Typical Fix: This code is almost always triggered by user error when upgrading the electrical system. Disconnecting the battery to install a high-capacity AGM battery, wiring up a winch, or tapping into the main power for a custom switch panel will cause this. Simply driving the Jeep for a few days through normal heat cycles will clear it.