P0615
Starter Relay CircuitP0615 is a generic OBD-II powertrain diagnostic trouble code: Starter Relay 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 P0615 means
P0615 is stored when the PCM (or BCM, on vehicles where the body control module manages starter engagement) detects an abnormal voltage or open-circuit condition on the starter relay control circuit. In this architecture the control module provides a switched ground or a switched voltage signal to energize the starter relay coil; when the PCM commands a start and the feedback voltage on that circuit does not match expectations, the code is logged. On push-button-start and auto-stop/restart platforms the PCM commands the relay electronically on every start event, making the circuit more heavily exercised and more likely to expose marginal connections.
The practical consequence ranges from an illuminated check engine light with no other symptom (the vehicle starts normally but the circuit shows intermittent glitching) to a complete no-crank, no-start condition. An audible click from the relay location without the starter motor engaging is a telltale sign that the relay coil is receiving power but either the relay contacts or the downstream starter circuit is failing. P0615 should not be confused with codes that indicate the starter motor itself has failed — the code is specifically about the PCM-side control wire, not the high-current starter feed.
Diagnosis follows the control circuit from the PCM output driver through the relay to the starter solenoid. Common culprits are a faulty relay (welded or open contacts, failed coil), corroded connector pins at the relay socket or PCM, or a broken wire in the control harness. PCM internal output driver failures are less frequent but do occur, particularly on high-mileage modules that have experienced repeated voltage irregularities.
Common causes
Most-frequently reported root causes when P0615 is logged.
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1
Faulty starter relay with a burned coil, welded contacts, or mechanical sticking preventing proper energization.
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2
Corroded, loose, or broken connector pins at the relay socket, fusebox, or PCM harness connector.
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3
Open or short-to-voltage in the wiring between the PCM output driver and the relay control terminal.
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4
Poor battery-to-chassis or engine-to-chassis ground connection causing reference voltage shift on the control circuit.
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5
Failed PCM internal output driver transistor unable to sink current through the relay coil.
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6
Blown fuse or failed fusible link in the starter relay control circuit.
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7
Low system voltage from a weak battery or failing alternator preventing the relay coil from pulling in reliably.
Symptoms drivers notice
How to diagnose P0615
A typical diagnostic flow when this code is present.
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1
Connect a scan tool, record P0615 and all companion DTCs plus freeze frame data, then clear and attempt to reproduce the fault.
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2
Inspect the battery — verify state of charge and perform a load test; confirm system voltage is above 12.4 V at rest and above 10 V during cranking.
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3
Locate the starter relay in the engine-compartment fuse/relay box; visually inspect for corrosion, melting, or damaged socket terminals.
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4
Test the relay coil: apply 12 V directly across the coil terminals and verify the contacts click and have continuity; replace the relay if it fails.
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5
Probe the PCM-side control wire at the relay socket while a second person presses the start button — expect a switched ground (or switched 12 V, depending on design) from the PCM during the start command.
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6
Check harness continuity from the relay control terminal back to the PCM connector pin; repair any open or short found in the wiring.
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7
If wiring and relay test good, test the PCM output driver with a logic probe or oscilloscope; replace or reprogram the PCM if the driver is confirmed defective.
Related powertrain codes
- P0600 — Serial Communication Link Malfunction
- P0601 — Internal Control Module Memory Check Sum Error
- P0602 — Control Module Programming Error
- P0603 — Internal Control Module Keep Alive Memory (KAM) Error
- P0604 — Internal Control Module Random Access Memory (RAM) Error
- P0605 — Internal Control Module Read Only Memory (ROM) Error
Frequently asked questions
Will replacing the starter motor fix P0615?
Not unless the starter itself has caused a short that pulled the control circuit down. P0615 is a PCM-to-relay control wire fault, not a starter motor fault. Replacing the starter is an expensive and usually incorrect repair for this specific code.
Can P0615 appear on vehicles with push-button start?
Yes — push-button-start systems still use a starter relay that the PCM (or BCM) energizes electronically. In fact these systems are more likely to flag intermittent control-circuit faults because the relay is commanded programmatically on every start event rather than being held by a mechanical key position.
Is it safe to drive with P0615?
If the vehicle is currently starting and running, it can be moved to a shop, but the code indicates an intermittent or pending no-start condition. The vehicle may fail to restart after it is switched off, so prompt diagnosis is important.
Can a weak battery cause P0615?
Yes. Insufficient battery voltage can prevent the relay coil from pulling in fully, causing the PCM to see an unexpected voltage on the control circuit and log P0615. Always verify battery condition before pursuing wiring or PCM diagnosis.
Disabling P0615 in software
RaceTune can permanently disable P0615 — 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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