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Technical Description of OBD-II Trouble Code
The Exhaust Gas Recirculation A Control is Stuck Closed
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) that applies to OBD-II vehicles. This may include 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 P042F, 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 P042F code, the valve appears to be stuck in the closed position according to the PCM. 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 side effect of gasoline and diesel engine operation.
The main 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 various sensors such as the throttle position sensor (TPS), vehicle speed sensor (VSS), and crankshaft position sensor (CKP) to determine when to open or close the EGR valve.
Vehicles with this code typically have a step-down EGR valve that 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 P042F will be stored and the malfunction indicator lamp (MIL) may illuminate. Other vehicles use data from the manifold air pressure (MAP) sensor and/or the differential pressure feedback EGR (DPFE) sensor to determine the position of the EGR valve. Most vehicles require multiple ignition cycles with a failure before the MIL illuminates.
Photo of the exhaust gas recirculation (EGR) valve:
What is the severity of this DTC?
From a drivability standpoint, the closed position of the EGR valve does not present any serious issues. Therefore, a code P042F can be addressed at your earliest convenience.
What are some of the symptoms of the code?
Symptoms of a P042F EGR trouble code may include:
What are some of the common causes of the code?
Causes for this P042F code may include:
What are some P042F troubleshooting steps?
To diagnose a code P042F, you will need a diagnostic scanner, digital volt/ohmmeter, and a reliable vehicle information source.
Before diagnosing the code, it is recommended to visually inspect all EGR system related wiring and connectors. Replace 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 P042F 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 observe 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.
The DPFE and MAP sensors should indicate whether the EGR valve has opened or closed as desired. If there are MAP sensor or DPFE sensor codes present, they may be related to the P042F code and should be addressed accordingly.
If the desired EGR position differs from the actual position, 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 in question uses a DPFE sensor, follow the manufacturer’s recommendations for testing it. Consult connector pinout charts and vehicle wiring diagrams from your vehicle information source to aid in testing. Replace defective sensors as necessary and retest the system.
The DVOM can be used to test individual circuits between the PCM connector and the EGR valve connector. Disconnect all related controllers from the circuit before testing.
Professional Service
While we always recommend seeking mechanical solutions for this issue, if that is not possible, we offer the option to permanently delete this specific DTC. All other codes will continue to be addressed. If you are interested in this option, please upload your ECU file to our portal.
