Starter Request Circuit
Diagnostic trouble code P0512 indicates a malfunction within the starter request circuit, which is responsible for signaling the engine computer to engage the starter motor. The powertrain control module (PCM) sets this code when it detects an improper voltage level, an open circuit, or a short in the signal wire from the ignition switch.
This code is considered high severity because a failure in the starter request circuit can prevent the engine from cranking, potentially stranding the driver. It should be diagnosed and repaired immediately to ensure vehicle reliability.
Common symptoms
- Engine cranks intermittently or fails to crank at all
- Illuminated Check Engine Light
- No response when turning the ignition key or pressing the start button
- Audible clicking from the starter relay without engine rotation
- Starter motor continues to run after the engine has started (rare)
Likely causes
- Faulty ignition switch or push-button start switch
- Blown starter relay or ignition circuit fuse
- Corroded, damaged, or loose wiring in the starter request circuit
- Faulty neutral safety switch or clutch position switch interrupting the signal
- Internal failure in the Powertrain Control Module (PCM)
What to check before replacing parts
Check battery voltage and terminal connections
Look for: A fully charged battery (12.4V or higher) and clean, tight terminals to rule out basic power supply issues causing low voltage to the circuit.
Inspect the starter and ignition system fuses and relays
Look for: Blown fuses or a starter relay that fails to click or lacks continuity across its load terminals when energized.
Test the ignition switch or start button output
Look for: The correct battery voltage signal being sent down the starter request wire when the switch is moved to the 'Start' position.
Perform a continuity and resistance test on the starter request circuit wiring
Look for: High resistance, open circuits, or shorts to ground in the wiring harness between the ignition switch and the PCM.
Monitor the starter request PID using an advanced scan tool
Look for: The PCM data parameter to change from 'Off' to 'On' when the ignition switch is activated, verifying whether the computer is actually receiving the physical signal.
This page explains the generic P0512 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.