97 Lumina EGR Code

[airsense00]

Hello,

I am working on a few more codes to get my lumina back in shape. The first one is P0401. Here is what I read about that code:

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 EGR (DPFE). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0401 code means that OBD detected an insufficient amount of EGR.
Symptoms

You may notice drivability problems such as pinging (a.k.a. pre-ignition knock) when the engine is under load or the vehicle is at higher speeds. There may also be other symptoms.
Causes

A code P0401 most likely means one or more of the following has happened:

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

Possible Solutions

In fixing this code, it is quite common for people to just replace the EGR valve only to have the OBD code return. The EGR valve is not always the culprit.

• Use a vacuum pump and pull the EGR valve open while monitoring engine RPM's & DPFE voltage. There should be a noticable difference in RPM's with the EGR open
• Clean out the EGR valve and/or tubing to remove deposits
• Check the voltage at the DPFE, compare to specified values (refer to a repair manual for your specific model)
• Replace the DPFE sensor (with a good quality / OEM one)
• Replace the EGR valve

I was thinking of trying to replace the DPFE sensor. I am looking at the EGR valve and see an electrical connection coming out of the egr valve. Is the DPFE sensor all one unit with the EGR valve? I have already removed the EGR valve and cleaned it out using carb cleaner. The valve itself seems to be working fine.

[maxwedge]

The egr is pcm controlled and operates at different levels as it is pulse width modulated, a full function scanner can command the egr on and you will feel the engine stumble at low rpms if it is working, using a wiring diagram you can manually operate the valve by grounding the correct wire and do the same test.

[Cubsfan24]

I got the P0401 code in my 3.1L 96 Lumina with 142k miles. I searched around and found a video on youtube showing how to clean the passage way between the intake and EGR valve. Overtime it seems it gets clogged and sets off the code. I cleaned the port out and it was really dirty. The code hasn't come back on since cleaning so I think I fixed the problem. Here is the link to the video: http://www.youtube.com/watch?v=hpB6CELWYhQ

[wafrederick]

It does not have a DPFE sensor.One cause is a piece of carbon stuck holding the pintle valve open ands I have seen this happen.Carquest does sell an EGR gasket with a filter on it to prevent this.

[airsense00]

Hey thanks for the video on how to clean the port. I have already cleaned the valve but didnt think about the passageway. I have never removed a throttle body before, is there any tricks or things I can screw up removing that? I know I will have to get a new gasket.

[Cubsfan24]

As far as taking the throttle body off, that was the first time I took mine off also. I followed what that guy did in the video. The hardest part was the bottom bolt on the throttle body, you need to move that stiff tube out of the way to get to the actual bolt head. But to do that you have to disconnect the two small hoses on the bottom of the throttle body to this pipe and at the end of that pipe at the rear of the engine you have to diconnect it from another hose also to be able to bend/push the pipe out of the way to get to the bottom bolt for the throttle body. I thought I was going to break something when I had to push that pipe out of the way. Other than that it was fairly easy.

[airsense00]

Been meaning to tackle this but been out of town. Anyways tonight I did what the video said and tested the egr with the car running by hooking up some leads and I got the click noise so thats good but the idle did not change a bit, so just like the video mine is clogged up. One more question, when you cleaned the port what did you use to clean it? I don't have any throttle cables laying around. I was thinking some pipe cleaners?

[Cubsfan24]

The only wire I could find was a coat hanger. That didn't work out that well because I couldn't get the coat hanger to bend through the port. So I ended up using some weed wacker cable to break the passage free and spray a bunch of carb cleaner in the passage. You need a cable about as thick as a coat hanger but much more flexible. I had some really thick weed wacker cable and it seemed to work.

[airsense00]

Ok all done everything is put back together. I feel like I could do this easily now since I did it once... sometimes you just have to get your hands dirty... and dirty they got doing this...

I ended up using a combination of clothes hanger, pipe cleaners, and a tube with suctions kinda like a turkey baster, they are used for checking battery fluid I think. I pushed that down the egr side and keep squirting the carb cleaner till I broke through on the throttle side. Man was everything completely caked with grit. It seems the car is even running better now. I installed new gaskets on both the egr and throttle body. This ended up taking 3 hours by the time I figured it all out. I took my time. Well I cleared the code and crossing my fingers.. Next project is the cat converter code I am getting, but I think I am going to take it in for that one.

Thanks for all your tips and help, I love this site.