Technical Description of OBD-II Trouble Code
High Flow in Evaporative Emission System Leak Detection Reference Orifice
What does that mean?
This is a generic diagnostic trouble code (DTC) that typically applies to OBD-II vehicles equipped with an EVAP system that utilizes a leak detection system. This can include vehicles from Toyota, Scion, GM, Chevrolet, Hyundai, Pontiac, Volvo, and others. It is commonly observed in Toyota vehicles. The specific repair steps may vary depending on the year, make, model, and powertrain configuration.
The PCM has detected a discrepancy in the evaporative emissions system (EVAP) leak detection reference orifice, resulting in the storage of code P043F in your OBD-II vehicle. In this case, a high flow condition has been detected.
The EVAP system is designed to capture fuel vapors from the fuel tank before they are released into the atmosphere. It uses a vented reservoir, also known as a canister, to store excess vapors until the engine is operating under conditions that allow for efficient burning of the vapors.
The pressure generated by the stored fuel acts as a propellant, causing the vapors to vent through tubes and into the canister. The canister contains a charcoal element that absorbs fuel vapors and releases them at the appropriate time.
The EVAP system typically includes various sample orifices, a leak detection pump, a charcoal canister, an EVAP pressure sensor, a purge valve/solenoid, a vent control valve/solenoid, and a complex system of metal tubes and rubber hoses that stretch from the fuel tank to the engine compartment.
The EVAP system uses engine vacuum to draw fuel vapors from the charcoal canister and through the lines into the intake manifold, where they can be burned instead of being vented into the atmosphere. The PCM controls the purge control valve/solenoid, which regulates intake vacuum to the EVAP canister, allowing fuel vapors to be drawn into the engine only when conditions are optimal for efficient burning.
Some EVAP systems use an electronic leak detection pump to pressurize the system for leak and flow testing. Leak detection reference orifices may be placed at various points in the EVAP system. These orifices are typically in-line devices that allow for accurate measurement of flow when the leak detection pump is activated. The PCM uses input signals from EVAP pressure and flow sensors, along with the leak detection reference orifice(s), to determine if the leak detection system is functioning correctly. The EVAP leak detection reference orifice may be a small filter-type device or simply a section of the EVAP line that restricts flow, allowing an accurate sample to be obtained by an EVAP pressure/flow sensor.
If the PCM detects a high flow condition through the EVAP leak detection reference orifice, it will store code P043F and may illuminate the malfunction indicator lamp (MIL).
What is the severity of this DTC?
EVAP leak detection codes, including P043F, specifically relate to the evaporative emission control system and should not be considered severe.
What are some of the symptoms of the code?
Symptoms of a P043F trouble code may include:
What are some of the common causes of the code?
Possible causes for this P043F engine code may include:
What are some P043F troubleshooting steps?
Diagnosing a code P043F will require a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information.
Consult your vehicle information source to check for any relevant technical service bulletins (TSB) that match the symptoms and codes present in the vehicle being diagnosed. If a suitable TSB is found, it may provide guidance on the exact source of the malfunction, saving time and effort.
If there are other EVAP system codes present, address and repair those before attempting to diagnose the P043F code. The P043F code may be a reaction to conditions that have caused other EVAP codes.
Before performing any hands-on work, connect the scanner to the vehicle diagnostic port and retrieve all stored codes and freeze frame data. It can be helpful to write down this information as the diagnosis progresses. After retrieving the data, clear the codes and test-drive the vehicle to see if the code is reset.
Ideally, test-drive the vehicle until one of two things happens: either the PCM enters readiness mode or the code is reset. If the PCM enters readiness mode, it indicates an intermittent problem or an inadvertent repair, and there may not be much that can be done at this point. If the code is reset, it indicates a definite malfunction that needs to be identified and addressed.
Begin with a visual inspection of any accessible EVAP system-related wiring harnesses and connectors. Focus on areas of high temperature and areas where wiring, connectors, vacuum lines, and vapor hoses may come into contact with moving components. Many vehicle repairs are made during this inspection phase, so it is important to concentrate and put effort into it.
Connect the scanner to the vehicle diagnostic port and observe the data stream. When the EVAP system is activated, the EVAP flow and pressure data should meet the manufacturer’s specifications. In most cases, it is possible to activate the EVAP system (purge control solenoid and/or leak detection pump) using the scanner. Some EVAP sensor testing may need to be performed with the system activated.
Use the DVOM to test EVAP sensors and solenoids and compare the readings to the manufacturer’s specifications. Any components that do not align with the specifications should be replaced. If possible, inspect the EVAP leak detection reference orifice for charcoal contamination. If contamination is found, it may indicate a compromised EVAP canister.
Before testing system circuits with the DVOM, disconnect any related controllers to prevent damage. Test the resistance and continuity of circuits between individual EVAP components and the PCM using the DVOM. Repair or replace any circuits that do not meet the specifications.
