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P codepowertrainMedium severity

P0510Closed Throttle Position Switch

The closed throttle position (idle) switch is not reporting the throttle-closed state correctly to the engine computer.

Definition

The closed throttle position switch tells the PCM when the throttle is fully released, which the PCM uses to enable idle speed control, deceleration fuel cut, and idle ignition timing strategies. P0510 sets when the switch signal disagrees with throttle position sensor voltage — for example, the switch never closes at idle or stays closed off-idle. Symptoms include unstable or incorrect idle speed, poor deceleration behavior, hesitation on tip-in, and an illuminated MIL.

Common causes

  • Faulty or worn closed throttle position switch
  • Misadjusted switch or throttle stop screw
  • Throttle plate not returning fully closed due to carbon buildup or a binding cable
  • Open, shorted, or corroded wiring in the switch circuit
  • Skewed throttle position sensor causing a correlation mismatch
  • PCM input fault (rare)

Common misdiagnoses

  • Idle air control valve
  • Complete throttle position sensor replacement when only adjustment is needed
  • Throttle body assembly
  • PCM

Troubleshooting steps

  1. 1.Check switch state on a scan tool

    With the key on, the closed throttle switch parameter should read ON/closed at rest and switch OFF as soon as the pedal is slightly depressed.

  2. 2.Inspect the throttle plate and linkage

    Verify the throttle returns fully against its stop; clean carbon from the throttle bore and check the cable for binding or incorrect freeplay.

  3. 3.Test the switch directly

    Backprobe or ohm the switch: it should show continuity (or the specified voltage change) at closed throttle and open within the manufacturer's angle spec, typically within the first 1-2 degrees of opening.

  4. 4.Verify TPS correlation

    Confirm closed-throttle TPS voltage is within spec (commonly 0.3-0.9 V depending on application); a skewed TPS will fail the plausibility check even with a good switch.

  5. 5.Check wiring and adjust or replace

    Repair any opens or shorts in the switch circuit, then adjust the switch to specification or replace it and confirm the code does not reset.

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