Powertrain, generic · Auxiliary emission controls

P043F EVAP System Leak Detection Reference Orifice High Flow

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. Systems with a leak detection pump (Bosch DM-TL at VW, Audi, BMW and Maserati, Denso's canister pump module at Toyota/Lexus) first measure a reference value with the pump working only through a built-in 0.5 mm (0.020 in) orifice; it is the yardstick for the small-leak test that CARB requires. P043F means the reference measurement shows too much flow – the reference vacuum or pressure does not reach the expected value, because the reference path or changeover valve leaks, the pump is weak, or air enters through leaking valves in the test path. The leak test can then not be judged, since a weak yardstick would hide leaks. GM and Ford do not use the code.

Likely causes

Leak detection pump faulty (weak pump, leaking changeover valve, liquid damage)
Purge valve does not seal
Pump supply or connector (contact resistance, corrosion)
Leaking hose between pump module and canister

Symptoms

  • Check engine light on
  • EVAP leak test does not run, readiness not set
  • Usually no change in driving

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–600
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

evap leak detection pumpreference orificecharcoal canisterengine control module

Related codes

P043EP2401P2402P2419P0456

References: static.nhtsa.gov, patents.google.com, patents.google.com, law.cornell.edu.