Fix P043E: Mechanic’s solutions that WORKED

The code P043E: Evaporative Emission System Leak Detection Reference Orifice Low Flow points out a fault in the Evaporative Emission System, specifically relating to the leak detection reference orifice’s low flow. It’s typically caused by issues in the EVAP canister assembly, vent hoses, or related electrical connections.

P043E quick overview

Meaning	P043E: Evaporative Emission System Leak Detection Reference Orifice Low Flow
Is it serious?	This code can be moderately serious as it relates to the vehicle’s emissions system, which, if not addressed, can lead to increased environmental pollution and potentially more serious engine problems.
Possible causes	– Faulty or damaged EVAP canister assembly – Blockages or restrictions in the EVAP system hoses – Wiring or connection issues at the canister pump module or ECM – Water or fuel contamination in the EVAP system – Malfunctioning vent valve
How to diagnose?	Inspect EVAP Canister: Check the condition of the EVAP canister assembly and consider replacing if necessary. Check Vent Hoses and Filters: Ensure there are no blockages in the vent hoses and the filter is clear. Verify Electrical Connections: Examine connections at the canister pump module and ECM for any issues. Consider ECM Update or Issues: Explore the possibility of an ECM update or malfunction. Perform Smoke Test: Conduct a smoke test to detect any leaks in the EVAP system. Look for Contamination: Check for signs of water or fuel in the canister or other EVAP components.

How to fix P043E – learn from mechanics

I looked into P043E service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Volvo

Vehicle Information: 2015 Volvo XC60 T6 3.0L

Issue + Repair History:

• Hesitation and MIL lamp on.
• Repeat failures of the LDP (Leak Detection Pump).
• Charcoal canister filled with fuel.
• Customer advised against topping off the fuel tank, claims compliance since the first failure.
• Previous replacements of LDP and charcoal canister due to similar issues.

Other OBD2 Codes + Test Results:

• P043E – Evaporative Emission System Leak Detection Reference Orifice Low Flow.
• Automated test of fuel tank system failed, setting off P043E again.
• Fuel observed dripping from the electrical connector of the LDP.
• Charcoal canister found full of liquid fuel.

Suggestions to Fix Issue:

• Verify if the purge solenoid is leaking.
• Inspect if there is a check valve on top of the tank to prevent fuel from getting into the canister.
• Consider checking the Evap valve under the intake next to the throttle, in case it’s stuck open.
• Suggestion to check two rollover valves and one float limit vent valve connected to the canister.

Final Fix:

• The problem was traced back to incorrectly installed O-rings on the in-tank vent hose by a previous repair shop.
• New O-rings for the in-tank vent hose, along with the replacement of the charcoal canister and LDP, resolved the issue.

Case #2: Toyota

Vehicle Information: 2009 Toyota RAV4 Limited 2.5L

Issue + Repair History:

• MIL lamp on.
• EVAP system passes self-tests but returns with the same codes.
• Replaced EVAP canister assembly first with aftermarket, then with factory canister.
• Fuel cap tested marginal and replaced.
• Smoke tested for leaks, none found.
• Same codes reappeared after vehicle release.

Other OBD2 Codes + Test Results:

• P043E: Evaporative Emission System Leak Detection Reference Orifice Low Flow.
• EVAP system self-test failed, setting off P043E again.
• No apparent physical issues like water or dirt in the system.

Suggestions to Fix Issue:

• Check the vent valve or purge valve for faults.
• Test the 12-volt battery, as voltage drop can affect EVAP system test results.
• Consider possibility of purge valves sticking after getting hot.
• Suggestion of restriction in the system rather than a leak, potentially hidden crud in the canister filter.

Final Fix:

• Found that the EVAP system test pump was not creating vacuum.
• Replaced the pump, O-rings for in-tank vent hose, canister, and LDP.
• Dealership claimed water intrusion and performed tech bulletin, though no water was found previously.
• Ongoing uncertainty about the root cause; vehicle was sent to dealership for further repairs.

Case #3: Toyota

Vehicle Information: 2006 Toyota Tacoma 4.0L

Issue + Repair History:

• MIL lamp on with recurring EVAP codes.
• Vehicle sets codes P043E, P043F, P2401, P2402, P2419 after sitting overnight.
• Two canisters replaced, and a used PCM installed.
• Power, ground, and 5-volt reference wiring to canister checked and found good.
• EVAP tests pass with no codes when using a scanner.
• Ground wire showing more than the recommended resistance (50 Ohms).
• Replaced connector to the canister, but problem persisted.

Other OBD2 Codes + Test Results:

• P043E – Evap Leak Detection Reference Orifice Low (repeated multiple times).

Suggestions to Fix Issue:

• Check the wiring and connectors, especially behind the left kick panel.
• Review freeze frame data for additional clues.
• Correct the ground wire resistance issue.
• Load test the power wires to the canister from the ECM end.
• Consider potential rodent damage to the wiring harness.

Final Fix:

• Customer declined further repairs due to the truck needing other work of higher priority.
• A recommendation was made to rewire the canister.

Case #4: Pontiac

Vehicle Information: 2009 Pontiac Vibe 2.4L

Issue + Repair History:

• Check engine, traction, VSC, and AWD lights on.
• Initial codes: P043E, P043F, and low battery voltage/system charge.
• Toyota TSB #EG002-06 referenced (similar to Toyota Matrix).
• EVAP canister assembly replaced after noticing liquid in hoses.
• GM dealer unable to resolve low voltage and EVAP problems.
• Replaced canister, but issues persisted.

Other OBD2 Codes + Test Results:

• P043E – Evaporative Emission System Leak Detection Reference Orifice Low

Suggestions to Fix Issue:

• Check for faulty parts and request a warranty replacement.
• Consider the Toyota TSB for similar models, which suggests issues like water intrusion into the fuel evaporation system.
• Check the vent valve for being stuck open and the vacuum pump for inlet vacuum blockages.
• Suggestion to check the fuel tank pressure sensor.

Final Fix:

• Replaced the canister again, suspecting a faulty part.
• Redesigned the vent pipe by installing an in-line fuel filter and hose into the vent tube.
• Flushed water through the inlet hose to the canister and performed a smoke test.
• Checked the fuel tank pressure sensor for operation.

Case #5: Toyota

Vehicle Information: 2007 Toyota Corolla S 1.8L

Issue + Repair History:

• SES light on with five EVAP codes: P043E, P043F, P2401, P2402, P2419.
• Initially, connections at canister pump module and ECM checked; EVAP hoses blown out.
• Replaced canister assembly with Toyota part #77740-02130, but the same codes returned after 100 miles and one week.
• Dealer suspected ECM issue and planned to replace under warranty.

Other OBD2 Codes + Test Results:

• P043E, P043F, P2401, P2402, P2419 – all related to EVAP system.

Suggestions to Fix Issue:

• Check the VSV (purge valve) at the air intake.
• Ensure no restriction on the line to the vent, including the vent filter.
• Check for water intrusion through filler neck or improperly mounted tire splash shields.
• Consider possibility of ECM issue and reference any related TSBs or campaigns.
• Smoke test the system to ensure proper sealing and check for overfilled gas tank.

Final Fix:

• The Toyota dealer initially replaced the canister, suspecting a defective part.
• The EVAP codes returned, leading to the replacement of the ECM, which solved the problem.

Advice	Brief Description of Diagnostic Step
Check the EVAP Canister Assembly	Inspect and potentially replace the EVAP canister assembly.
Examine Vent Hoses and Filters	Blow out and ensure no blockages or restrictions in vent hoses, including the vent filter.
Verify Connections and Wiring	Check connections at canister pump module and ECM, ensuring no wiring issues.
Consider ECM Issues	Explore the possibility of an ECM (Engine Control Module) problem or update.
Smoke Test the EVAP System	Conduct a smoke test to identify leaks in the EVAP system.
Look for Water or Fuel Contamination	Check for water intrusion or fuel in the canister and related components.
Assess Vent Valve Function	Inspect the vent valve for proper operation and any blockages.