Clogged, restricted, or contaminated reference orifice in the EVAP canister or leak detection module; Failed or sticking EVAP canister vent valve that prevents proper reference flow; Faulty EVAP pressure sensor giving an inaccurate baseline reading; Damaged or pinched EVAP hose between the canister, vent valve, and reference orifice; Loose, missing, or leaking fuel cap or filler neck seal; Corroded or damaged wiring and connector pins at the EVAP module or sensor; Failed leak detection pump or module assembly on vehicles that use a pump-style system

DTC codes / P04xx · Auxiliary emission controls / P043E

P043EEVAP System Leak Detection Reference Orifice Low Flow

Q: What does code P043E mean?

EVAP System Leak Detection Reference Orifice Low Flow. P043E means the engine computer detected that the EVAP (evaporative emission) system's leak detection reference orifice is flowing less than expected during the self-test. The computer uses a calibrated orifice as a baseline to judge whether the fuel system can hold pressure or vacuum, and this code sets when the reference measurement itself is out of range.

P043E means the engine computer detected that the EVAP (evaporative emission) system's leak detection reference orifice is flowing less than expected during the self-test. The computer uses a calibrated orifice as a baseline to judge whether the fuel system can hold pressure or vacuum, and this code sets when the reference measurement itself is out of range.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illuminated check engine light, often with no other symptoms
A pending or stored P043E code with no driveability complaints
Occasional fuel odor around the rear of the vehicle if a leak is present
Difficulty completing an EVAP monitor or passing an emissions inspection
Rough idle or hesitation only if a related vacuum or purge fault is also present
No noticeable change in fuel economy or performance in most cases

Common causes, most likely first

Clogged, restricted, or contaminated reference orifice in the EVAP canister or leak detection module
Failed or sticking EVAP canister vent valve that prevents proper reference flow
Faulty EVAP pressure sensor giving an inaccurate baseline reading
Damaged or pinched EVAP hose between the canister, vent valve, and reference orifice
Loose, missing, or leaking fuel cap or filler neck seal
Corroded or damaged wiring and connector pins at the EVAP module or sensor
Failed leak detection pump or module assembly on vehicles that use a pump-style system

How to diagnose and fix it

Inspect the fuel cap and filler neck for looseness, cracks, or missing seals and correct as needed
Check all EVAP hoses and connections for cracks, pinches, or disconnects, especially around the canister and vent valve
Use a scan tool to command the EVAP vent valve and leak detection pump and verify they operate and seal correctly
Remove and inspect the reference orifice and canister for debris, spider webs, or fuel contamination, cleaning or replacing as required
Compare the EVAP pressure sensor reading to a known-good value or a mechanical gauge to confirm sensor accuracy
Perform a smoke test on the EVAP system to locate any leak that could skew the reference measurement
Repair or replace the faulty EVAP canister, vent valve, leak detection module, or sensor and clear the code, then run the EVAP monitor to confirm the repair

Why the reference orifice matters more than the leak

Many technicians replace the canister or vent valve without first checking the reference orifice for debris, which is a common cause of this code on vehicles that sit or are driven on dusty roads.
A weak or failing EVAP pressure sensor can report a low-flow reference condition even when the orifice and plumbing are completely clear, so sensor verification should come before parts replacement.
P043E is often accompanied by other EVAP codes such as P0455 or P0456, and diagnosing the reference fault first can prevent unnecessary leak repairs.
The EVAP monitor may not run for several drive cycles after a repair, so the code can reappear temporarily even when the fix is correct until the monitor completes.
On some vehicles the reference orifice is integrated into the leak detection module and cannot be serviced separately, making module replacement the only correction.

Can I keep driving with P043E?

This code does not affect engine performance or safety, so the vehicle can be driven normally while you arrange diagnosis. Avoid topping off the fuel tank past the first click and schedule service soon, since an unresolved EVAP fault will prevent the emissions monitor from completing and may cause a failed inspection.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.