The OBD2 code P043F, typically indicative of an “Evaporative Emission System Leak Detection Reference Orifice Low Flow,” points to issues within the vehicle’s EVAP system. This system is designed to capture and recycle fuel vapors, preventing them from escaping into the atmosphere. Issues flagged by this code can lead to a lit malfunction indicator lamp (MIL) but may not always affect the vehicle’s immediate drivability.
P043F quick overview
| Meaning | P043F: Evaporative Emission System Leak Detection Reference Orifice Low Flow |
| Is it serious? | Moderate. While it might not affect the vehicle’s performance, it’s crucial for emissions control and fuel efficiency. |
| Possible causes | – Faulty or clogged charcoal canister – Defective EVAP canister pump module – Blocked vent hoses – ECM software needing an update |
| How to diagnose? | Inspect the charcoal canister for damage or clogs. Check vent hoses for blockages or disconnections. Evaluate the canister pump module for proper operation. Consult relevant TSBs for known issues and fixes. Consider ECM evaluation for software updates or replacement. |
P043F Meaning
P043F signals a snag in the system that recycles fuel vapors, potentially leading to environmental harm and reduced fuel economy.
It often involves a deep dive into the EVAP system, checking everything from the charcoal canister that stores these vapors to the hoses and valves that manage their flow. Resolving it might require replacing specific parts like the canister or updating the car’s computer software.
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How to fix P043F – learn from mechanics
I looked into P043F 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: Toyota
Vehicle information 2006 Toyota Corolla CE 1.8L
Issue + repair history
- Came in with MIL lamp on.
- No drivability issues observed.
- TSB EG002-06 suggests replacing the charcoal canister assembly if DTCs P043E, P043F, P2401, P2402, and P2419 are all present.
- Charcoal canister assembly replaced but MIL lamp came back on after 900 miles.
Other OBD2 Codes + Test Results
- P043E
- P043F
- P2401
- P2402
- P2419
Mechanic suggestions
- Check fuel level and for liquid fuel entering the canister, possibly due to overfilling.
- Inspect the canister purge solenoid valve and fuel pressure regulator for malfunction.
- Run the Automatic Evap test after replacing the canister to confirm repair.
- Review TSB EG040-06 which suggests replacing the EVAP pump module.
- Verify wiring connections and voltages at the charcoal canister.
- Monitor vapor pressure sensor voltage and suspect a faulty ECM if necessary.
- Check for water contamination in the canister due to overfilling or deep water.
- Investigate the possibility of water entry via the filler neck, considering TSB EG047-06.
Final fix
- Cleared the codes and followed up with the customer, and the MIL lamp remained off.
Case #2: Toyota
Vehicle information 2007 Toyota Corolla S 1.8L
Issue + repair history
- SES light on with five EVAP codes: P043E, P043F, P2401, P2402, P2419.
- Vent hoses between canister and filler neck were blown out.
- Canister assembly replaced with Toyota part #77740-02130, but codes returned after 100 miles.
- Dealer replaced canister again, thinking the replaced one was defective, but codes returned.
- Appointment at the Toyota dealer scheduled for ECM replacement under warranty.
Other OBD2 Codes + Test Results
- P043E
- P043F
- P2401
- P2402
- P2419
Mechanic suggestions
- Check the VSV (purge valve) at the air intake for failures.
- Ensure the canister was replaced as a complete assembly with the vent valve and leak detection pump.
- Inspect for any restrictions in the vent line, including the vent filter, and check for water contamination, possibly due to water intrusion through the filler neck or improperly mounted tire splash shields.
- Consider an updated ECM, as suggested by some technicians.
- Check for TSBs related to replacing the canister and ECM for these codes.
- Smoke test the system and verify the gas cap is sealing properly, as overfilling the gas tank could lead to fuel entering the canister and causing leaks.
Final fix
- Toyota dealer replaced the canister again, followed by ECM replacement, which solved the problem.
Case #3: Lexus
Vehicle information 2007 Lexus RX350 3.5L
Issue + repair history
- Poor fuel economy, MIL lamp on.
- Customer’s frequent schedule limits proper diagnostic testing.
- Considering replacing fuel cap and vent valve without thorough diagnosis.
- Installed a new canister with the pump, awaiting customer feedback.
Other OBD2 Codes + Test Results
- P2401: Evaporative emission leak detection pump stuck off
- P2402: Evaporative emission leak detection pump stuck on
- P2419: Evaporative emission pressure switching valve stuck on
- P043F: Evaporative emission system leak detection reference orifice low flow
Mechanic suggestions
- Replace the canister assembly, as the canister has a high failure rate.
- Consider replacing the charcoal canister/pump assembly due to common failure.
- Replace the canister assembly, as the leak detection pump often fails, causing these codes.
- Suggest proper diagnostic testing, although challenging due to the customer’s schedule.
- Provide resources for diagnostic procedures to aid in proper diagnosis.
- Emphasize replacing the Evap canister assembly, as it frequently fails and is easy to diagnose with appropriate tools.
Final fix
- Installed a new canister with the pump assembly, awaiting customer feedback.
How to diagnose P043F
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Explanation |
|---|---|
| Inspect charcoal canister | Look for physical damage or signs of clogging. |
| Check vent hoses | Ensure no blockages or leaks could impede vapor flow. |
| Evaluate canister pump module | Verify the module’s operation; consider replacement if faulty. |
| Consult TSBs for fixes | Follow manufacturer recommendations for parts replacement or software updates. |
| Consider ECM evaluation | Update software or replace the ECM as necessary based on diagnostics. |
In these service cases, the recurring theme is addressing EVAP system components, notably the charcoal canister and related valves or modules, guided by diagnostics and TSB recommendations. Despite replacing canisters and other parts, some cases required ECM replacements to fully resolve the issue, highlighting the importance of a comprehensive approach that includes both hardware and software considerations in the vehicle’s EVAP system management.
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko