P0512 Starter Request Circuit Malfunction

P0512 points to a starter request circuit malfunction. The controller is not seeing the expected start request signal from the ignition switch, start button, relay, or body control path.

Code details

Generic OBD-II · P0

System: Speed / Idle
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the starter motor for P0512 until the request signal and relay control circuit have been verified.

Symptoms of P0512

Unstable, high, or low idle, or stalling.
Erratic speedometer, cruise-control, or shift behaviour.
Check-engine light with a hesitation or surge.

Common causes of P0512

A dirty throttle body, idle-control valve, or throttle-position sensor.
A failing vehicle-speed or wheel-speed sensor, or its wiring.
Vacuum leaks or a related sensor forcing the idle/speed strategy.

Useful checks before replacing parts

Compare start request data, ignition switch state, park/neutral input, immobilizer status, starter relay command, battery voltage, and freeze-frame data.
Inspect ignition switch or start button wiring, relay control, fuse feeds, BCM or PCM communication, clutch or neutral safety inputs, and grounds.
Verify whether the starter request reaches each module and whether the relay output matches the command.

Related OBD-II codes

These nearby speed / idle entries can help compare wording and pin down the fault area.