What does EGR vacuum modulator do?
The EGR vacuum modulator is a component found on some EGR systems. It controls the flow of the EGR system by using a vacuum operated diaphragm to increase or decrease EGR flow. For vehicles equipped with them, the EGR vacuum modulator is one of the most important components of the EGR system.
How serious is a P0401 code?
How serious is the P0401 code? A failed EGR valve can cause the engine to have excessive ignition pre-ignition that can cause internal engine damage to the piston and valves. The Check Engine Light on will cause the vehicle to fail emission testing from excessive NOx gases.
What does p0401 EGR system insufficient flow detected mean?
So you have changed the EGR valve and this p0401 code continues to pop up on the computer. You are frustrated and ready to drive your car off of a cliff. What does this P0401 diagnostic trouble code mean anyway? The correct definition for this diagnostic trouble code P0401 is “ Insufficient EGR Flow Detected “.
What to do if your EGR valve is insufficient?
Most folks see P0401 Insufficient EGR flow, look up the price of an EGR valve, see how cheap it is and just throw a new one on. That can be a mistake. That’s because the EGR valve is not always going to be the culprit. Here are some of the most common fixes to help clear the P0401:
What causes a p0401 code on a PCM?
Here are the common causes of P0401: 1 Clogged EGR passages 2 Faulty EGR valve 3 A failed sensor (e.g., differential pressure sensor, manifold absolute pressure sensor, etc.) 4 Inadequate vacuum supply to the EGR valve 5 Circuit problems, such as damaged wiring and loose connections 6 Issues with the PCM, such as software in need of an update
Where are the EGR and dpfe sensors located?
The EGR valve position sensor is located right on the EGR valve itself while the DPFE sensor (Digital Pressure Feedback EGR) is separate from the EGR valve. It uses two hoses attached to the exhaust or exhaust manifold.