P0468

What it means

P0468 means the engine control unit has detected a voltage from the evaporative emissions purge flow sensor circuit that is higher than expected. The purge flow sensor (fitted only on some vehicles) monitors how much fuel vapour is drawn from the charcoal canister into the intake. The fault sets when the signal voltage stays above the permitted range, which points to the sensor, its wiring or the control unit input.

Symptoms

• Check engine light on
• Possible failed emissions test or evaporative system readiness monitor not completing
• Fuel smell around the car in some cases
• Slightly rough idle or hesitation after refuelling if purge flow is affected
• Often no noticeable change in driving

Possible causes

• Faulty purge flow sensor giving a high or out-of-range signallikely
• Signal wire shorted to a voltage supply, or damaged wiringlikely
• Corroded, loose or damaged connector terminals at the sensor or control unitpossible
• Open circuit in the sensor ground return, which pushes the signal highpossible
• Purge valve stuck open or a blocked or restricted purge line affecting the sensor readingpossible
• Fault within the engine control unit input circuitrare

How to diagnose

1. Read all stored and pending codes and review the freeze frame data for engine load, temperature and fuel level when the fault set
2. Check for other evaporative or purge valve codes, as these help narrow down the cause
3. Visually inspect the sensor, its wiring harness and connectors for chafing, heat damage, water ingress and corrosion
4. Inspect the purge hoses and canister connections for cracks, blockages or disconnection
5. Check live data for the purge flow sensor signal with the ignition on and with the engine running, and compare it with the manufacturer's specification
6. Using the wiring diagram for the specific model, test the sensor supply voltage, ground and signal wire for shorts to voltage or open circuits
7. Command the purge valve on and off with a diagnostic scan tool and check that the sensor signal responds as expected
8. Check that the sensor is mounted and its connector is fitted correctly, as the layout and sensor type vary by make and engine

How to fix

• Replace the purge flow sensor if it gives a faulty signal and the wiring tests good
• Repair or replace damaged wiring and fix any short to voltage or open circuit
• Clean or replace corroded connectors and terminals
• Repair the ground connection if the return path is open
• Replace a stuck purge valve or clear or replace restricted purge lines
• Clear the code after repair and run a drive cycle to confirm the fault does not return

Can I keep driving?

Nearby codes

• P0467GenericEVAP Purge Flow Sensor Circuit Low
• P0469GenericEVAP Purge Flow Sensor Circuit Intermittent