P043E: EVAP Leak Detection Reference Orifice Low Flow
P043E means the evaporative emission (EVAP) system's self-test found too little airflow through its built-in reference opening, usually because that opening or its passage is partly blocked by dirt or liquid. It rarely changes how the car drives, but it turns on the check engine light and stops the EVAP leak test from running.
You can keep driving
The code usually causes no change in driving and limp mode is not expected. The check engine light stays on and the EVAP system can't test itself, so fix it before an emissions inspection.
What it means
The EVAP system traps fuel vapor from the tank in a charcoal canister and feeds it to the engine later through a purge valve. A vent valve opens the canister to fresh air. Some cars have a leak detection pump that first runs against a built-in 0.5 mm (0.020 in) opening, which serves as a yardstick for the small-leak test. With P043E, the measurement through that opening shows too little flow: the vacuum, or on some systems the pressure and pump current, rises higher than expected. The computer reads this as a partly blocked orifice or reference path, often from dirt or from liquid after overfilling the tank. Because the yardstick can't be trusted, the leak test is not run. GM and Ford do not use this code.
Likely causes
- Reference orifice or pump module dirty or blocked by liquidVery likely
Overfilling the tank or splashed water can push liquid or dirt into the small opening, which restricts the flow.
- Faulty leak detection pumpPossible
A weak or blocking pump, or a stuck changeover valve, can produce the same too-low flow reading.
- Engine module softwareLess likely
The software can sometimes misjudge the reading and set the code falsely.
- Pump connector or electrical supplyLess likely
A poor connection or a dip in voltage can change the pump's behavior during the test.
What you may notice
- Check engine light on
- EVAP leak test does not run and the readiness status is not set
- Usually no change in driving
What to check, cheapest first
- 1Think back: was the tank recently overfilled past the first click of the pump, or did water get splashed under the car? This points toward a liquid-blocked orifice. · you can do it
- 2Look at the leak detection pump or canister module connector for corrosion, looseness or damage, and check that it is fully seated. · you can do it
- 3Read the stored codes and freeze-frame data, and check whether related codes such as P043F, P0442 or P0456 are also present. · mechanic
- 4Check whether a software update is available for the engine module, since false detection has been fixed that way. · mechanic
- 5Measure the pump's supply voltage and run the pump test with a scan tool to see the reference reading and pump current. · mechanic
- 6Inspect the pump module for dirt or liquid, then clean or replace the module, clear the code and run a drive cycle to confirm the test completes. · mechanic
Related codes
Frequently asked questions
Can I drive with P043E?+
Yes. The code usually doesn't affect driving. The light stays on and the EVAP test can't run, so have it fixed before an emissions test.
Can a loose gas cap cause P043E?+
Unlikely. This code is about the reference opening inside the test system, not a leak. A loose cap is more typical of leak codes such as P0442 or P0456.
Will P043E pass an emissions test?+
Probably not. The check engine light is on and the EVAP readiness status is not set, which can lead to a failure.
Can overfilling the tank cause this code?+
Yes. Liquid fuel or water reaching the pump module or reference orifice is the most common cause listed for this code.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10