P0402 OBD-II Trouble Code

Technical Description

Exhaust Gas Recirculation Flow (EGR) Excessive Detected

What does that mean?

EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor (DPF). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0402 code means that OBD detected an excessive amount of EGR.

Symptoms

You may notice drivability problems such as the engine may surge off idle. There may also be other symptoms.

Causes

A code P0402 most likely means one or more of the following has happened:

• The DPFE (differential pressure) sensor is faulty and needs to be replaced
• There is a blockage in the EGR (most likely carbon buildup)
• The EGR valve is faulty
• The EGR valve may not be opening due to a lack of vaccuum

Possible Solutions

With a P0402, it is common for people to replace the EGR valve, only to have the problem return. The most likely solution is to replace the DPFE sensor.

• Check the voltage at the DPFE sensor both at idle and when the EGR is open
• Replace the DPFE sensor

More Information

• FordF150.net Forums
• California State University Case Study

Need more help?

If you still need help regarding the P0402 trouble code, please post your concern in the forums.

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