EVAP canister purge valve codes

How its codes differ

• P0443 is an electrical fault in the purge valve circuit: check wiring and the valve's coil.
• P0441 means the computer commanded purge and did not see the change it expected (for example in fuel trim), so flow is wrong even though the circuit seems fine.
• P0496 means vapour is flowing when the valve should be closed, which points to a valve stuck open.
• A purge valve stuck open can also stop the system sealing for the leak test, so it can sit behind leak codes such as P0456. On some Ford models a service bulletin links a stuck purge valve to hard starting or stalling right after refuelling.
• P0497 (low purge flow) can be a valve that does not open when commanded.
• P0440, P0442 and P0455 can involve a purge valve that leaks or sticks; VW bulletin 20 17 02 says to smoke test and check vacuum before replacing the valve.
• A valve stuck open lets vapour and air into the intake when it should be closed, which can disturb fuel trim and set P0175 or P0171.

Codes

• P0441

  EVAP purge flow incorrect

  Severity: Monitor

• P0443

  EVAP purge valve circuit fault

  Severity: Monitor

• P0496

  EVAP purge flow when purge should be off

  Severity: Monitor

• P0456

  EVAP system very small leak detected

  Severity: Monitor

• P0440

  EVAP system fault (general)

  Severity: Monitor

• P0442

  EVAP system small leak detected

  Severity: Monitor

• P0455

  EVAP system large leak detected

  Severity: Monitor

• P0497

  EVAP system low purge flow

  Severity: Monitor

• P0171

  Engine computer has reached its limit adding fuel on bank 1: the mixture is lean

  Severity: Monitor

• P0175

  Engine computer has reached its limit removing fuel on bank 2: the mixture is rich

  Severity: Monitor

Signs it's failing

• Check engine light with P0441, P0443, P0496 or a leak code
• Rough idle
• Hard starting or stalling, especially right after refuelling on some vehicles
• Running rich

How to test it

1. Inspect the valve's connector and the hoses to the canister and intake for cracks or disconnection. (Use caution)

   Warning: Fuel vapour is flammable. Work with the engine off and cool, away from sparks or flames.

2. Check whether the valve holds when it should be closed: with the engine off, vacuum or air applied to the valve should not pass through. Use service information for your vehicle's exact test. (Use caution)

   Warning: Fuel vapour is flammable. Work with the engine off and cool, away from sparks or flames.

3. Commanding the valve with a scan tool and watching fuel trim or tank pressure respond needs a capable scan tool; a shop can do this. (Best left to a shop)

   Warning: Fuel vapour is flammable; testing with the engine running should be done by a trained technician.

After the repair

• Clear codes and let the EVAP monitor run; it may need specific fuel level and temperature conditions, so allow several days of normal driving.
• Clear codes only after the repair, then drive normally over several days with both city and highway driving so the readiness monitors can complete; clearing codes or disconnecting the battery resets them to not ready, which fails an emissions test.
• Check that hard starting after refuelling has stopped.