P0512
Starter Request CircuitP0512 is a generic OBD-II powertrain diagnostic trouble code: Starter Request Circuit. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0512 means
P0512 is stored when the ECM detects that the starter request signal circuit is reading a voltage lower than expected. The starter request circuit carries the signal from the ignition switch or start button to the ECM, which then authorises and controls starter motor engagement.
A low voltage condition on this circuit typically points to a short to ground somewhere in the wiring between the ignition switch or start control module and the ECM, or a faulty switch that is holding the circuit low unintentionally. In some systems it can also indicate an internal ECM fault affecting the input circuit.
The practical consequence is that the ECM may not correctly detect a start request, causing no-start conditions or intermittent starting problems. Because the starter circuit interacts with the immobiliser and BCM in many modern vehicles, companion network codes or immobiliser codes may also be present. Always record all codes before beginning diagnosis.
Common causes
Most-frequently reported root causes when P0512 is logged.
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1
Short to ground in the starter request signal wire between the ignition switch and ECM.
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2
Faulty ignition switch or start button holding the circuit in a low state.
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3
Damaged or corroded connector at the ignition switch, BCM, or ECM.
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4
Wiring harness chafing causing an unintended ground contact.
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5
Failed ECM input circuit for the starter request signal.
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6
Relay or control module in the start circuit failing and pulling the line low.
Symptoms drivers notice
How to diagnose P0512
A typical diagnostic flow when this code is present.
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1
Read and record all DTCs from all modules, noting any immobiliser or network codes.
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2
Inspect the starter request circuit wiring and connectors for damage, corrosion, or chafing.
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3
Measure the voltage on the starter request circuit at the ECM connector with the ignition in the off position.
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4
Disconnect the ignition switch or start button and recheck the circuit voltage to isolate the source of the low signal.
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5
Check for a short to ground along the harness routing between the switch and ECM.
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6
Verify ECM pin integrity and check for reference voltage supply to the ECM.
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7
Repair any identified wiring fault or replace the ignition switch if confirmed faulty.
Related powertrain codes
Frequently asked questions
Can I bypass the starter circuit to test if the ECM is the problem?
Bypassing safety circuits is not recommended as it can damage components or create safety hazards. Use proper diagnostic procedures with a multimeter and scan tool.
Is P0512 related to push-button start systems?
Yes. P0512 applies to both traditional ignition key systems and modern push-button start systems, as both use a starter request signal circuit to the ECM.
Could a dead key fob battery cause P0512?
A dead key fob would typically set an immobiliser code rather than P0512. P0512 is specifically about the electrical circuit carrying the start request signal.
Will the engine start if P0512 is set?
It depends on whether the ECM can still interpret the start request. Some vehicles will have intermittent starting issues; others may have a complete no-start.
Disabling P0512 in software
RaceTune can permanently disable P0512 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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