Technical Description of OBD-II Trouble Code
The exhaust gas recirculation A control is stuck open.
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) that applies to OBD-II vehicles. This includes vehicles from various manufacturers such as Ford, Chevrolet / GM / Cummins, Dodge / Ram, Isuzu, Pontiac, Toyota, BMW, Mercedes, etc. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
If your vehicle has stored a code P042E, 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 the P042E code, the PCM perceives that the valve is stuck in the open position. The designation A refers to a specific position or stage of the step-down EGR valve control system, which is explained further below.
The EGR system is responsible for allowing the engine to consume a portion of the unburned fuel from the exhaust system. This system is necessary to reduce the levels of nitrogen oxide (NOx) emissions produced as a byproduct of gasoline and diesel engine operation.
The key component of the EGR system is an electronically controlled (EGR) valve 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 it is appropriate to open or close the EGR valve.
Vehicles with this code typically have a step-down EGR valve. The step-down EGR valve operates in stages based on factors such as throttle position, engine load, and vehicle speed.
In some models, the PCM also monitors the position of the EGR valve plunger. If the actual position of the EGR valve differs from the desired position commanded by the PCM, a code P042E will be stored and the malfunction indicator lamp (MIL) may illuminate. In most cases, the MIL will not illuminate until there have been multiple ignition cycles with a failure.
Photo of exhaust gas recirculation EGR valve:
What is the severity of this DTC?
The conditions that lead to a stored code P042E may also cause significant drivability issues. Therefore, it is important to address a code P042E promptly.
What are some of the symptoms of the code?
Symptoms of a P042E EGR trouble code may include:
What are some of the common causes of the code?
Possible causes for this P042E code may include:
What are some P042E troubleshooting steps?
To diagnose a code P042E, you will need a diagnostic scanner, digital volt/ohmmeter, and a reliable source of vehicle information.
Before diagnosing a code P042E, it is recommended to visually inspect all EGR system related wiring and connectors. Replace or repair any corroded or burned components as necessary.
Next, connect the scanner to the diagnostic port and retrieve all stored codes and freeze frame data. Take note of this information, as it may be helpful if the P042E code is intermittent. Clear the codes and test drive the vehicle to see if the code is reset.
If the code is reset, reconnect the scanner and monitor the data stream. Check the desired EGR position (typically measured in percentage) and compare it to the actual EGR position displayed on the data stream. They should be identical within a matter of milliseconds. If the actual EGR position indicates that it is open too far, it is possible that carbon has clogged the plunger opening or that the EGR valve is defective.
If the EGR valve can be easily removed for inspection, it is recommended to do so, especially if the vehicle has more than 100,000 miles. Carbon fouling and passage clogging are common issues in high-mileage vehicles. If the plunger appears to be impaired, remove the obstruction and retest the EGR system.
If no obstruction is found in the EGR valve plunger opening, follow the manufacturer’s recommendations for testing the EGR actuator solenoids using a DVOM. Step-down EGR valves may use multiple solenoids to control the full spectrum of EGR system operation.
If the EGR system for the vehicle includes an EGR valve position sensor, it is likely integrated into the valve itself. Follow the manufacturer’s recommendations, as well as the connector pinout charts and vehicle wiring diagrams found in your vehicle information source, to test individual components. Replace any defective parts as necessary and retest the system.
Use a DVOM to test individual circuits between the PCM connector and the EGR valve connector. Disconnect all related controllers from the circuit before testing.
