P042E Exhaust Gas Recirculation A Control Stuck Open
What does it mean?
This is a generic powertrain diagnostic trouble code (DTC) that applies to OBD-II vehicles. It may include, but is not limited to, vehicles from Ford, Chevrolet/GM/Cummins, Dodge/Ram, Isuzu, Pontiac, Toyota, BMW, Mercedes, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.
If your vehicle has stored a P042E code, it means that the powertrain control module (PCM) has detected a problem with the exhaust gas recirculation (EGR) valve control system.
In the case of P042E, the valve appears (to the PCM) to be stuck in the open position. The designation A applies to a particular position or step of the lowered EGR valve control system, which is explained below.
The EGR system is responsible for allowing the engine to consume some of the unburned fuel from the exhaust system. The EGR system is necessary to reduce harmful levels of nitrogen oxides (NOx) created as a byproduct of gasoline and diesel engine operation.
The focal point of the EGR system is an electronically controlled valve (EGR) that opens to allow exhaust gases to re-enter the engine intake. The PCM uses input signals from the throttle position sensor (TPS), vehicle speed sensor (VSS), and crankshaft position sensor (CKP) to determine when conditions are suitable for opening/closing the EGR valve.
Vehicles that exhibit this type of code are equipped with a lowered EGR valve. The lowered EGR valve operates in stages based on the degree of throttle opening, the amount of load placed on the engine, and the speed at which the vehicle is moving.
In some models, the position of the EGR valve piston is also monitored by the PCM. If the desired EGR valve position (as commanded by the PCM) is different from the actual position, a P042E code will be stored and a malfunction indicator light (MIL) may illuminate. Most vehicles will require several ignition cycles (with a fault) before the MIL illuminates.
Photo of the Exhaust Gas Recirculation EGR Valve:
How severe is this DTC?
Conditions that lead to a stored P042E code can also cause serious driving problems. For this reason, a P042E code should be addressed urgently.
What are some of the symptoms of the code?
Symptoms of a P042E EGR fault code may include:
- Irregular engine idle
- Reduced fuel efficiency
- Excessively lean exhaust
- Other drive codes may be stored
What are some common causes of the code?
Causes of this P042E code may include:
- Faulty EGR valve
- EGR valve piston clogged with carbon or other debris
- Faulty EGR control solenoid/valve
- Open or shorted wiring/connectors in the EGR A control circuit
- Faulty DPFE sensor
- Bad EGR valve position sensor
- PCM malfunction or PCM programming error
What are the P042E troubleshooting steps?
A diagnostic scanner, a digital volt/ohmmeter, and a reliable source of vehicle information are among the tools needed to diagnose a P042E code.
Visual inspection of all cables and connectors related to the EGR system is an ideal precursor to diagnosing a P042E code. Repair or replace any corroded or burnt components as needed.
Continue by connecting the scanner to the diagnostic port and retrieving all stored codes and freeze frame data. Note all of this as it will prove useful if the P042E is an intermittent code. Now, clear the codes and test-drive the vehicle to see if the code resets.
If the code resets, connect the scanner and observe the data stream. Check the desired EGR position (usually measured as a percentage) and the actual EGR position, as shown on the data stream display. Within milliseconds, they should be identical. If the actual EGR position indicates it is open too far, suspect that a piece of carbon has clogged the piston opening or that the EGR valve is faulty.
Obviously, the simplest method to inspect the EGR plunger would be to remove the valve and take a look. Unfortunately, the location of the EGR valve on some models makes the removal (and reinstallation) of the EGR valve less than convenient. If the EGR valve can be easily removed for inspection, that would be my first step (especially if the vehicle in question has over 100,000 km). Carbon fouling and clogged passages are fairly common issues for high-mileage vehicles. If the piston appears to be obstructed, remove the blockage and test the EGR system again.
If no obstruction is found in the EGR valve piston opening, follow the manufacturer’s recommendations for testing the EGR actuator solenoids with the DVOM. Lowered EGR valves may use multiple solenoids to affect the full spectrum of EGR system operation.
If the EGR system for the vehicle in question uses an EGR valve position sensor, it is likely integrated into the valve itself. Follow the manufacturer’s recommendations, along with connector pinout charts and vehicle wiring diagrams found in your vehicle information source, to test individual components. Replace faulty parts as needed and test the system again.
The DVOM can be used to test individual circuits between the PCM connector and the EGR valve connector. All associated controllers must be disconnected from the circuit before testing begins.
*Carbon deposits are caused by the high levels of detergent found in modern fuels
*Once repairs are made, allow the PCM to enter readiness mode before assuming they were successful.