P043E: EVAP System Leak Detection Reference Orifice Low Flow

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.

Symptoms

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

Most 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)

What to check, in order

Start with the simplest. You can tick off each step.

1. Start with the fuel cap: tighten it fully and check its seal
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Inspect the hoses and connections around the tank and the charcoal canister
4. Use the scanner to test the purge and vent solenoid valves
5. Run a smoke test to find small leaks

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P043E means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 4: Emissions
• 3E: Specific fault in that system

Frequently asked questions

Can I keep driving with code P043E?

Yes, you can normally keep driving. If there is a strong smell of gasoline, find the leak before continuing and do not smoke nearby.

What causes code P043E?

The most common causes are: 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).

Related codes

• P043FEVAP System Leak Detection Reference Orifice High Flow
• P2401EVAP System Leak Detection Pump Control Circuit Low
• P2402EVAP System Leak Detection Pump Control Circuit High
• P2419EVAP System Switching Valve Control Circuit Low
• P0456EVAP System Leak Detected (very small leak)
• P0442EVAP System Leak Detected (small leak)

Sources

• static.nhtsa.gov: MC 10213825 9999
• static.nhtsa.gov: SB 10053936 1988
• patents.google.com: US6964193
• patents.google.com: US6845652

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.