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P256D Powertrain

Engine Idle Speed Selector Sensor/Switch Circuit High

Idle-speed selector input reads stuck high — short to battery voltage or analog signal at maximum. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.

Affected components

  • Idle speed selector switch

Common causes

  • High likelihood: Switch wire shorted to battery voltage
  • Low likelihood: Connector pins corroded - high contact resistance
  • Low likelihood: Supply wire pinched against B+ source

Possible symptoms

  • Check engine light on
  • Idle speed too high, too low, or unstable
  • Possible stalling at idle or after cold start

Diagnostic notes

  • The malfunction indicator lamp may illuminate

Related codes

Sources

Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.

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