EVAP Purge Flow Sensor Circuit Intermittent

Possible causes

• CommonFailed pressure sensor
• CommonCorroded or water-ingressed connector - much of this system is under the vehicle
• CommonBlocked, split or perished sensing hose
• CommonDamaged wiring underneath, including rodent damage
• PossibleLoss of reference voltage or earth
• PossibleLoose or missing fuel cap, so the pressure genuinely is wrong
• CommonPurge valve stuck open or closed

What you might notice

• Check engine light on
• Failed emissions test
• EVAP leak tests not completing
• Fuel smell in some cases
• Usually no drivability symptom
• Rough idle if the purge valve is stuck open

What to check, in order

1. Read all codes. Purge flow codes alongside this one suggest the flow really is wrong and the sensor is reporting correctly.
2. Check the fuel cap first. A loose, damaged or missing cap is the single most common cause of EVAP faults and costs nothing to check.
3. Inspect the connector for corrosion and water - these sensors are mounted underneath and take constant road spray.
4. Check the sensing hose for splits, kinks and blockage.
5. Check the reference voltage and earth at the sensor.
6. Note that EVAP monitors run only in particular conditions of fuel level, temperature and time since start, so confirming a repair can take several journeys.