Trouble Code P0402: EGR Excessive Flow Detected

What Is Excessive Exhaust Gas Recirculation Flow?

Your EGR system works with your exhaust emissions system to recirculate exhaust gas and reduce emissions. This system is made of three basic components. First, the EGR valve creates a seal until it’s ready to be opened. The actuator solenoid opens your EGR valve once it’s activated. Finally, a differential pressure sensor is used to determine the amount of recirculation needed.

If you see trouble code P0402, it means that your vehicle’s computer system has recognized, through the differential pressure sensor, that the EGR has excessive flow. Unless the issue is a faulty sensor, excessive flow could affect the performance of your engine. A faulty sensor may still cause your EGR valve to open or close improperly, leading to additional flow. This issue is particularly troublesome at idle, when the valve would prevent your engine to surge.

Symptoms

Now that you understand your EGR system, what does the code P0402 mean? Some typical symptoms that you’ll experience as the EGR improperly recirculates additional emissions are issues with surging, particularly when idling. You’ll also see your malfunction indicator light and your OBD-II scanner will read trouble code P0402.

Even if you don’t experience engine issues, finding the solution can prevent further damage to your vehicle. Inspect your EGR system and restore any damaged components to restore your fuel economy, prevent engine damage and avoid sudden surges.

Typical Causes

Unlike other trouble codes, there are only three basic parts to consider when you see this code. The differential pressure sensor, EGR valve and actuator solenoid are the only likely causes for this trouble code.

Your differential pressure sensor can be damaged or working incorrectly. Because of the small circuits and complex parts within this sensor, a damaged sensor will need to be replaced rather than repaired. A faulty sensor may or may not cause performance issues, depending on the actuator solenoid and EGR valve.

Your EGR valve can experience a number of issues that would trigger this error code. Carbon buildup can create blockage, as can other debris. A fault in the valve may cause it to improperly seal. Finally, a lack of vacuum in your entire EGR system will prevent the valve from sealing correctly.

Similarly, an actuator solenoid can become damaged, short circuit or experience wire damage that prevents it from operating effectively. The solenoid is essential for operating your EGR valve, so damage to an actuator solenoid will have similar symptoms to a damaged EGR valve.

Potential Solutions

Your make and model of vehicle may have specific steps to take for a proper repair. Always refer to your service manual and any relevant technical service bulletins before proceeding with more general repair solutions.

Many individuals immediately turn to the EGR valve to clear the code and restore the EGR system. While there are a number of issues that could point to the valve, it’s important to also inspect the differential pressure sensor and actuator solenoid.

Visually inspect the entire EGR system for any cracks, signs of blockage or signs of faulty electrical wiring. Test the voltage to your differential pressure sensor, when your EGR system is open and at idle, in order to rule out a sensor issue. If your sensor is working correctly, the most likely culprit is the EGR valve.
There are many other error codes related to your OBD-II scanner error code P0402 problem. Clearing this code may also clear trouble code P0400, P0401, P0403 and more. If these solutions don’t remove error code P0402, check any possible solutions for these related error codes to determine the cause and find a proper solution.