Closed Throttle Position Switch
The P0510 code indicates that the Powertrain Control Module (PCM) has detected a malfunction in the closed throttle position switch circuit. The computer sets this code when the switch fails to send the correct voltage signal confirming that the throttle plate is in the fully closed (idle) position.
While you can usually still drive the vehicle, a faulty closed throttle position switch can cause unpredictable idling or stalling at stops. It should be diagnosed and repaired soon to ensure safe and reliable operation.
Common symptoms
- Illuminated Check Engine Light
- Engine idles higher than normal
- Rough or erratic idle
- Engine stalling when coming to a stop
- Hesitation or stumbling upon initial acceleration
Likely causes
- Faulty closed throttle position switch
- Carbon buildup in the throttle body preventing the throttle plate from closing fully
- Damaged, corroded, or loose wiring and connectors in the switch circuit
- Misadjusted throttle position sensor or switch
- Failed Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Inspect the wiring harness and connector at the throttle position switch for damage, corrosion, or loose connections.
Look for: Broken wires, pushed-out pins, or heavy corrosion that would cause an open or short circuit.
Remove the intake boot and inspect the throttle body for heavy carbon buildup.
Look for: Carbon deposits holding the throttle plate slightly open, preventing the closed throttle switch from engaging.
Use a multimeter to test the closed throttle position switch for continuity when the throttle is fully closed.
Look for: The switch should show continuity (closed circuit) when the throttle is resting on its stop, and an open circuit as soon as the throttle is moved.
Check for proper reference voltage and ground at the switch connector with the key on, engine off.
Look for: Typically a 5-volt reference and a solid ground; missing voltage indicates a wiring or PCM issue.
Verify the mechanical adjustment of the throttle position switch or sensor if it is an adjustable type.
Look for: The switch must physically click or engage exactly when the throttle returns to the idle stop screw.
This page explains the generic P0510 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.
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