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P0469EVAP Purge Flow Sensor Circuit Intermittent

The signal from the EVAP purge flow sensor is cutting in and out, indicating an intermittent fault in its circuit.

Definition

On vehicles equipped with a purge flow sensor, the PCM monitors the sensor's signal to confirm how much fuel vapor is being drawn from the charcoal canister into the intake during purge events. P0469 sets when that signal drops out or changes erratically for brief periods rather than failing steadily low or high. Symptoms are usually limited to an illuminated MIL, though erratic purge feedback can occasionally cause minor idle instability during purge cycles, and the stored code will cause an emissions-test failure in most inspection programs.

Common causes

  • Chafed or intermittently open wiring in the purge flow sensor harness
  • Corroded or loose terminals at the sensor connector
  • Failing purge flow sensor with an internal intermittent fault
  • Poor ground connection for the sensor circuit
  • Electromagnetic interference from a nearby ignition or charging component
  • Intermittent fault in the PCM sensor input (rare)

Common misdiagnoses

  • EVAP purge solenoid valve
  • Charcoal canister
  • Gas cap
  • EVAP vent valve

Troubleshooting steps

  1. 1.Record freeze frame and monitor the sensor live

    Watch purge flow sensor data on a scan tool while commanding the purge valve on and off; look for signal dropouts or spikes that do not track the commanded duty cycle.

  2. 2.Wiggle-test the harness and connector

    With live data displayed, flex the sensor harness and tap the connector; any glitch in the reading pinpoints an intermittent connection.

  3. 3.Inspect connector terminals

    Disconnect the sensor and check for spread, corroded, or backed-out terminals; verify terminal tension with a matching test pin.

  4. 4.Check circuit continuity and shorts

    Measure signal, reference, and ground wires end-to-end for resistance under 1 ohm while flexing the harness, and confirm no intermittent short to ground or voltage.

  5. 5.Substitute or bench-test the sensor

    If wiring proves sound, replace the purge flow sensor, then run the EVAP monitor to confirm the code does not reset.

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