P0512 - Starter Request Circuit
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0512 is set when the Powertrain Control Module (PCM) detects an implausible signal from the starter request circuit. This circuit communicates the driver's intent to engage the starter motor. If the PCM detects a 'start' signal while the engine is already running at a certain RPM or if the signal persists for an abnormally long duration (typically >30 seconds), the code is stored. This is often caused by a short circuit to voltage or a sticking ignition switch/starter relay.
Possible Causes
Faulty ignition switch or start button (mechanically or electrically sticking)
Short circuit to voltage in the wiring harness between the ignition and PCM
Faulty starter relay (welded contacts)
Internal Powertrain Control Module (PCM) failure
Symptoms
Recommended Solution
- Visual Inspection: Ensure the ignition switch springs back freely from the 'Start' position. Check the starter relay for signs of overheating or melting.
- Measurement: Check voltage at the starter request pin on the PCM. It should read 0V in 'ON' position and Battery Voltage (~12.6V) only when 'START' is commanded.
- Diagnosis: Use a scan tool to monitor 'Starter Request' Live Data. If it shows 'Active' when it shouldn't, disconnect the ignition switch to see if the signal drops to 'Inactive'.
- Action: Replace faulty ignition switch, starter relay, or repair shorted wiring.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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