Fault code P043E – evaporative emission system leak detection reference orifice low flow

Fault code P043E is called “Evaporative Emission (EVAP) System Leak Detection Reference Orifice Low Flow” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P043E

This diagnostic trouble code (DTC) is a generic code. Error P043E is considered a generic code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.

Fault code P043E – evaporative emission system leak detection reference orifice low flow

This code indicates that the PCM has detected a mismatch in the fuel vapor recovery system (EVAP) check port or diaphragm. In this case, the error indicates low flow.

The emission control system (EVAP) prevents fuel vapor from escaping from the vehicle’s fuel system. The fuel vapors are routed through hoses to a carbon storage canister. Later, when the engine is running, a purge control valve opens, allowing fuel vapors to be drawn in under vacuum.

In some EVAP systems, an electronic leak detection pump is used to pressurize the system. Therefore, the system can be checked for leaks or flow.

Leak detection reference holes can be placed either at one point or at multiple points throughout the EVAP system. Leak detection holes are usually linear so that flow can be accurately measured when the pump is activated.

The PCM uses the input signals from the EVAP pressure and flow sensors in conjunction with the reference orifice to determine if the system is working properly.

The EVAP leak detection reference orifice is usually small, with a filter or just a section of the EVAP line. It restricts the flow so that the EVAP pressure or flow sensor can get an accurate sample.

If the PCM detects a low flow condition, through the EVAP system leak detection reference hole, code P043E will be stored. The Malfunction Indicator Light (MIL) may also illuminate.

Symptoms of vehicle malfunctions

The main signal that an error P043E has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. Activation of the Check engine indicator on the instrument panel.
  2. Possible perceptible fuel odor caused by vapor emission.

EVAP leak detection codes, such as P043E, relate exclusively to the fuel vapor control system and cannot be classified as serious.

Factors that can cause this error code

The error code P043E can mean that one or more of the following problems have occurred:

  • EVAP pressure sensor is defective.
  • Damaged EVAP line.
  • Damaged or clogged EVAP leak detection port.
  • Carbon element or canister is damaged.
  • Faulty vent or purge control solenoid.
  • Defective leak detection pump.
  • Sometimes faulty PCM module is the cause.

How to fix or reset OBD-2 code P043E

Some suggested steps for troubleshooting and fix the error code P043E:

  1. Repair damaged EVAP lines.
  2. Repair open or shorted voltage supply circuit to EVAP pressure sensor.
  3. Repair circuit going to PCM.
  4. Repair or clean the connector.
  5. Replace the EVAP pressure sensor.
  6. Repair or repair the restriction in the EVAP line.
  7. Replace PCM if the situation requires it.

Diagnose and repair of problems

When starting the P043E fault diagnosis, make sure that all EVAP hoses are connected correctly and in good condition. Check the wiring harnesses for obvious damage, due to fraying or improper routing. Inspect electrical connectors for corrosion, pins should be straight and properly installed.

Make sure that the exhaust hose that carries fresh air into the canister is not blocked, clogged or crushed. If insufficient air is drawn in during the purge cycle, it may cause this fault code to activate.

Visual Inspection

Because code P043E is a general fault code, it can often be related to damaged or corroded wiring. Also with a faulty or disconnected sensor.

Locate the EVAP canister under the vehicle. It may be attached to the fuel tank or be separated from it by the hoses going to the fuel pump. Make sure that the EVAP control pressure sensor connector is fully inserted and secured.

Inspect the connector for corrosion, disconnect the sensor and inspect the terminal pins. To make sure they are clean and free of moisture. Inspect the wiring from the sensor to determine if there are any tears, blows on the wire insulation. Which may indicate corrosion inside the wire.

Check the voltage on the sensor

Make sure there is 5 volts on the test lead, and check for continuity of the ground circuit. Check the sensor signal wire with a multimeter to determine the voltage, it should be about 3 volts.

Remove the hose attached to the EVAP pressure sensor and create a vacuum with a vacuum gauge, monitoring the voltage changes on the multimeter. If the voltage changes when the vacuum is applied, the sensor is working. If the voltage does not change, the sensor is defective.

Perform a wiggle test to determine if there is a problem. By jiggling or wringing the wires, watch the readings on the multimeter to see if there are voltage fluctuations. If the voltage rises or drops sharply when you turn a section of wire, you probably have a break that needs to be repaired.

If the jiggle test fails, disconnect the EVAP pressure sensor and check the voltage. If the voltage remains high with the sensor disconnected, check the wiring harness for a shorted signal wire.

If the reference voltage and ground readings are good, a faulty EVAP pressure sensor is most likely the problem. Therefore, you will have to replace it to correct error P043E.

Sometimes the high voltage disappears when the sensor is disconnected, the grounding circuit is good, and the reference voltage is correct. This indicates that the EVAP purge hose is clogged. Disconnect the hose from the purge valve and blow it out with compressed air. If the clog cannot be cleared, replace the hose.

On which vehicles does this problem occur most frequently

Fault code P043E can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Chevrolet
  • Chrysler (PT Cruiser)
  • Hyundai
  • Lexus
  • Pontiac
  • Scion
  • Toyota (Camry, Corolla, Matrix, Prius, RAV4, Yaris)
  • Volvo (XC90)

Fault code P043E can sometimes be found with other errors. The most common are the following: P043F, P2401, P2402, P2419.


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