P042E Diagnostic Trouble Code: Exhaust Gas Recirculation (EGR) “A” Control Stuck Open

Fault code P042E is called “Exhaust Gas Recirculation (EGR) “A” Control Stuck Open” 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 P042E

This code refers to a malfunction of the exhaust gas recirculation (EGR) system. The exhaust gas recirculation system is an integral part of the vehicle exhaust system. Its function is to prevent the formation of NOx (nitrogen oxides) in the cylinders.

P042E Diagnostic Trouble Code: Exhaust Gas Recirculation (EGR) "A" Control Stuck Open

If code P042E is still present in the vehicle, then the Powertrain Control Module (PCM) has detected a problem with the Exhaust Gas Recirculation (EGR) valve control system. In this case, the valve was stuck in the open position. The designation “A” refers to the downshift position of the EGR valve control system.

EGR is controlled by the vehicle’s computer, which opens or closes the EGR system depending on load, speed, and temperature. To keep the cylinder head at the proper temperature.

There are two wires that control and communicate with the computer. There are a total of 5 wires to the solenoid. Another 2 are battery voltage and ground. As well as one reference terminal for 5 volts, usually located in the center.

Cars with this code are equipped with an EGR step-down valve. The EGR step-down valve operates in stages depending on the degree of throttle opening, engine load and vehicle speed.

If the desired position of the recirculation valve differs from the actual position, trouble code P042E will be stored. The malfunction indicator lamp (MIL) may also illuminate. Most vehicles will require several ignition cycles with the malfunction before the MIL indicator light will go off.

Unleaded fuel is prone to NOx (nitrogen oxide) formation at extreme engine cylinder temperatures. The exhaust gas recirculation system sends a controlled amount of exhaust gas back to the intake manifold.

This is done to sufficiently dilute the incoming fuel mixture. This is to reduce the cylinder head temperature below the temperature at which NOx is generated.

Proper operation of the exhaust gas recirculation system is not only necessary to prevent NOx emissions. It also provides the engine with more power without detonation and a leaner fuel mixture for better fuel economy.

Symptoms of vehicle malfunctions

The main signal that an error P042E has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. Check engine control lamp on the control panel will light up (the code will be written to the ECM memory as a fault).
  2. Engine stalls or starts poorly.
  3. Floating revolutions, as well as attempts to stall at idle.
  4. The vehicle engine may become unstable.
  5. Increased fuel consumption.
  6. Decrease of the engine power.
  7. Sometimes there may be no symptoms, despite the stored fault code.

The severity of the code P042E is high, but if there are no other symptoms besides the fault indication, the problem is considered to be moderate. But this should not become a factor for not solving the problem.

Factors that can cause this error code

The error code P042E can mean that one or more of the following problems have occurred:

  • Short circuit to the ground.
  • Wiring problem or damaged connector.
  • Corrosion of electrical wires or connections.
  • Clogged exhaust gas recirculation valve channels.
  • Defective electronic differential pressure sensor with feedback (DPFE).
  • Faulty exhaust gas recirculation valve position sensor or absolute intake manifold air pressure sensor.
  • Excessive carbon buildup that prevents free movement of the valve (EGR).
  • Defective EGR.
  • In rare cases, malfunction of the control module (PCM).

How to fix or reset OBD-2 code P042E

Some suggested steps for troubleshooting and fix the error code P042E:

  1. Connect an OBD-II scanner to the vehicle’s diagnostic connector and read all stored data and error codes.
  2. Clear the error codes from the computer memory and test-drive the vehicle to see if error code P042E appears again.
  3. If the error code appears again, visually inspect the electrical wires and connectors related to the exhaust gas recirculation system.
  4. If necessary, repair or replace any shorted, broken, damaged, or corroded components.
  5. Check the operation of the exhaust gas recirculation valve and the vent control solenoid valve.
  6. Check the operation of the differential pressure sensor.
  7. Measure voltage across system vent control solenoid valve circuit using a digital multimeter.
  8. Compare value to manufacturer’s data sheet, replace faulty valve if necessary.
  9. If problem persists, check and replace module (PCM) if necessary.

Diagnose and repair of problems

The first step in the P042E troubleshooting process is to review the Technical Service Bulletins (TSB). For known problems with a particular vehicle.

The advanced diagnostic steps are very vehicle specific. It may require, special equipment and knowledge to accurately perform the steps.

Allow your vehicle’s engine to cool down. In most cases, exhaust gas recirculation (EGR) systems are very hot. Since they are usually installed directly on the exhaust system. Therefore, if you don’t let the engine cool down, you could get burned.

Be sure to carefully check the integrity of the wiring harnesses involved. They often run along and around the exhaust pipe. Therefore, it would be a good idea to tie off any loose wires. If you find a burned wire, solder the connections and make sure they are properly insulated.

Inspect the vent solenoid for cracks and water intrusion. Also, make sure that the connectors are properly electrically connected and that the latches are not damaged or broken.

Checking the recirculation valve

If available with access, you can remove the exhaust recirculation valve to check its condition. These valves are susceptible to significant soot buildup. Use carburetor cleaner and a toothbrush to remove soot from any soiled areas.

When there is no obstruction in the EGR valve plug hole, follow the manufacturer’s recommendations for testing the EGR actuator solenoids. Reducing EGR valves can use more than one solenoid. To affect the full range of operation of the EGR system.

If the exhaust recirculation system uses a position sensor for the recirculation valve, it is most likely built into the valve itself. Follow the manufacturer’s recommendations, as well as the vehicle’s wiring diagrams, to check individual components.

If necessary, replace defective parts and recheck the system for error P042E.

On which vehicles does this problem occur most frequently

Fault code P042E can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • BMW
  • Chevrolet (Cobalt, Cruze, Equinox)
  • Dodge (RAM)
  • Ford (F-150, Focus, Transit)
  • Isuzu
  • Land Rover (Freelander)
  • Mercedes-Benz
  • Pontiac
  • Suzuki (Forenza)
  • Toyota (Land Cruiser)
  • Volvo (V70)

Fault code P042E can sometimes be found with other errors. The most common are the following: P042F, P049A, P049B, P049C, P049D, P049E.

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