Fault in the leak detection pump or its reference orifice (where fitted), such as a split diaphragm, blockage or internal leak; Leaking or damaged EVAP hose, pipe or quick-release connector near the detection unit; Faulty or stuck purge valve or vent valve causing abnormal flow during the test; Damaged or loose fuel filler cap, or a damaged filler neck seal; Wiring or connector fault on the leak detection pump, vent valve or pressure sensor circuit; Cracked or saturated charcoal canister or damaged canister housing; Faulty EVAP pressure sensor giving a false reading.

P043F

EVAP System Leak Detection Reference Orifice High Flow.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
3F: FaultThe specific fault in that area

What it means

P043F is the generic code for the EVAP system leak detection reference orifice showing higher flow than expected. During the self-test, the control unit checks the system against a calibrated reference orifice of a known small size, and the measured flow, pressure or vacuum change was outside the expected range. This usually points to a fault in the leak detection hardware or a large leak affecting the reference check, rather than a small leak in the tank or lines.

Symptoms

Malfunction indicator lamp on
Usually no change in how the car drives
Fuel smell around the car or fuel filler area
Fuel filler cap warning message on some models
Failed emissions test or monitor not ready

Possible causes

Fault in the leak detection pump or its reference orifice (where fitted), such as a split diaphragm, blockage or internal leaklikely
Leaking or damaged EVAP hose, pipe or quick-release connector near the detection unitlikely
Faulty or stuck purge valve or vent valve causing abnormal flow during the testpossible
Damaged or loose fuel filler cap, or a damaged filler neck sealpossible
Wiring or connector fault on the leak detection pump, vent valve or pressure sensor circuitpossible
Cracked or saturated charcoal canister or damaged canister housingrare
Faulty EVAP pressure sensor giving a false readingrare

How to diagnose

Read all stored and pending codes and the freeze frame data, and note any other EVAP codes that point to a specific component
Check that the fuel cap is fitted, tightened properly and has an intact seal, and inspect the filler neck
Visually inspect the EVAP hoses, pipes and connectors between the tank, canister, purge valve and leak detection unit for splits, perishing or disconnected joints
Inspect the wiring and connectors of the leak detection pump, vent valve, purge valve and pressure sensor for damage, corrosion or water ingress
Use a bi-directional scan tool to operate the purge and vent valves and check they click, open and seal as commanded
Check live pressure sensor data for plausible readings with the system at rest and during the commanded test
Smoke test the EVAP system at low pressure to locate any leak, following the manufacturer's procedure for the model
Check the leak detection unit and canister for blockage, damage or contamination, as the layout and test method vary by make and model

How to fix

Replace the faulty leak detection pump or reference orifice assembly where it is serviced separately
Repair or replace leaking or damaged EVAP hoses, pipes or connectors
Replace a faulty purge valve or vent valve
Fit a correct, undamaged fuel filler cap or repair the filler neck seal
Repair damaged wiring or connectors in the affected circuit
Replace a damaged canister or faulty pressure sensor once testing has confirmed it
After repair, clear the code and complete a drive cycle to confirm the EVAP monitor runs and passes

Can I keep driving?

Low severity

The car can normally be driven as usual, as this fault does not usually affect engine running or safety. Book it in for repair soon to clear the warning light, stop fuel vapour escaping and avoid an emissions test failure.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.