DTC codes / Mazda codes / P1605
P1605 on Mazda vehicles means the Powertrain Control Module (PCM) has detected a failure in its Keep Alive Memory (KAM) self-test. The PCM runs this test at key-off or power-up to verify that learned values such as idle trim and fuel trims are retained; when the test fails, the module cannot trust its stored adaptive memory.
Guidance is general and written for Mazda vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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