What does it mean?
This is a generic diagnostic trouble code (DTC) that generally applies to OBD-II vehicles with an EVAP system that uses a leak detection system. This may include, but is not limited to, vehicles from Toyota, Scion, GM, Chevrolet, Hyundai, Pontiac, Volvo, etc. Anecdotally, this code appears to be much more common on Toyota-brand vehicles. Although generic, the exact repair steps may vary by year, make, model, and powertrain configuration.
The PCM has detected an anomaly in the leak detection reference orifice of the Evaporative Emission (EVAP) system when a P043E code is stored in your OBD-II vehicle. In this case, a low flow condition has been indicated.
The EVAP system is designed to capture fuel vapors (from the fuel tank) before they escape into the atmosphere. The EVAP system uses a vented reservoir (commonly called a canister) to store excess vapors until the engine is operating under the right conditions to burn them as efficiently as possible.
The pressure (developed when fuel is stored) acts as the propellant, causing the vapors to leak through the tubes and eventually into the canister. A charcoal element, contained in the canister, absorbs the fuel vapors and holds them for release at the appropriate time.
An assortment of sample orifices, a leak detection pump, a charcoal canister, the EVAP pressure sensor, the purge valve/solenoid, the vent control valve/solenoid, and a complex system of metal tubes and rubber hoses (extending from the fuel tank to the engine compartment) are typical components of the EVAP system.
Engine vacuum is used by the EVAP system to draw fuel vapors (from the charcoal canister and through the lines) into the intake manifold where they can be burned instead of being released into the atmosphere. The PCM electronically controls the purge control valve/solenoid, which is the gateway of the EVAP system. It is responsible for regulating the intake vacuum in the EVAP canister so that fuel vapors can be drawn into the engine only when conditions are ideal for the fuel pressure vapors to be burned as efficiently as possible.
Some EVAP systems use an electronic leak detection pump to increase pressure in the system, so that the system can be tested for leaks/flow. Leak detection reference orifices may be placed at a single point or at multiple points throughout the EVAP system. Leak detection reference orifices are typically of the inline variety so that a precise degree of flow can be measured with the leak detection pump activated. The PCM uses input signals from the EVAP pressure and flow sensors, in conjunction with the leak detection reference orifice(s), to determine if the leak detection system is functioning properly. The EVAP leak detection reference orifice may be a small filter-like device or simply an area of the EVAP line that restricts flow so that an EVAP pressure/flow sensor gets an accurate sample.
If the PCM detects a low flow condition through the EVAP leak detection reference orifice, a P043E code will be stored and a Malfunction Indicator Lamp (MIL) may be illuminated.
How severe is this DTC?
EVAP leak detection codes, similar to P043E, pertain exclusively to the evaporative emission control system and should not be classified as severe.
What are some of the symptoms of the code?
Symptoms of a P043E trouble code will most likely result in few or no visible symptoms. You may see slightly decreased fuel economy and other EVAP leak detection diagnostic codes.
What are some of the common causes of the code?
Causes
of this P043E engine code may include:
Faulty EVAP pressure sensor
A damaged or clogged EVAP leak detection orifice
Broken charcoal element (canister)
Cracked or crushed EVAP or vacuum line(s)
Faulty vent control or purge control solenoid
Bad leak detection pump
What are the P043E troubleshooting steps?
A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information will prove necessary to diagnose a P043E code.
Use your vehicle information source to check for Technical Service Bulletins (TSBs) that match the symptoms and codes present in the diagnosed vehicle. If you can find the appropriate TSB, it will likely direct you to the exact source of the malfunction without costing you much time and trouble.
If other EVAP system codes are present, diagnose and repair them before attempting to diagnose P043E. P043E could be in response to conditions that caused other EVAP codes.
Before getting your hands dirty, connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. I like to note this information as it may be useful as my diagnosis progresses. After that, clear the codes and test drive the vehicle to see if the code resets.
Ideally, you want to test drive the vehicle until one of two things happens; the PCM enters readiness mode or the code resets. If the PCM enters readiness mode, you have an intermittent problem (or you inadvertently fixed it) and there’s not much you can do now. If it comes back later, the failure condition may have worsened and you can start over. If the P043E resets, you know you have a hard and fast malfunction and it’s time to dig in and find it.
Start with a visual inspection of all wiring harnesses and connectors related to the EVAP system that you can reasonably access. Obviously, you’re not going to remove major components to take a look, but focus your efforts on high-temperature areas and areas where wiring, connectors, vacuum lines, and vapor hoses may interfere with moving components. Many cars are repaired during this phase of the diagnostic process, so focus and put some effort into it.
Connect the scanner to the vehicle’s diagnostic port and observe the data stream. EVAP flow and pressure data should conform to the manufacturer’s specifications when the system is activated. In most cases, activating the EVAP system (purge control solenoid and/or leak detection pump) may be possible using the scanner. Some EVAP sensor testing will need to be done with the system activated.
Use the DVOM to test the EVAP sensors and solenoids to compare them with the manufacturer’s specifications. All related components that do not meet specifications will need to be replaced. If possible, access the EVAP leak detection reference orifice to check for charcoal contamination. If charcoal contamination is detected, suspect that the EVAP canister has been compromised.
Before testing system circuits with the DVOM, disconnect all associated controllers to prevent damage. Test the appropriate levels of resistance and continuity between individual EVAP components and the PCM using the DVOM. Circuits that do not meet specifications will need to be repaired or replaced.
A loose or faulty fuel cap will not cause a P043E code to be stored
This code is applicable only to vehicle EVAP systems that use a leak detection system