Powertrain, generic · Auxiliary emission controls

P043E EVAP System Leak Detection Reference Orifice Low 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. P043E means the reference measurement shows too little flow – the vacuum (or with DM-TL the pressure and pump current) becomes stronger than expected, so the orifice or reference path is partly blocked, often by dirt or liquid after overfilling. GM and Ford do not use the code; Maserati fixed false triggering with software.

Likely causes

Reference orifice or pump module dirty or blocked by liquid (overfilled tank, splash water)
Leak detection pump faulty (weak or blocking pump, changeover valve stuck)
Engine module software (false detection)
Pump connector or supply (voltage dip)

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€0–600
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

P043FP2401P2402P2419P0456P0442

References: static.nhtsa.gov, static.nhtsa.gov, patents.google.com, patents.google.com.