Rough Idle and throwing p0402 code

Hi folks -

Well, my check engine light came on for the first time since I bought it in 2001.

Checked the code with my trusty scan guage and found the following code: P0402

According to OBD ll records, this indicates "EGR Excessive Flow Detected"

What can I do about this? Can it simply be removed and cleaned or do I need a new EGR?

I did a search here and only found one post regarding that code and it was simply a list of all the codes OBD ll can issue.

Anyone else experience this problem?

Symptoms:

Rough idel the past day or two, this morning while driving it seemed like it was gonna stall out on me while stopped but it never did. At speed, everything seems fine.

I did some research and found the following:

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


Thanks for any assistance you can provide on this matter :)

Clean the EGR and the tube that leads to the intake.

Thanks for the suggestion Tone :)

However, I have an update.

I was on my way to work this AM when I first noticed this happening. Half way through the day I decided to go get a coffee. When I got in the VX and started it up, the idle was much worse and this is when the check engine light actually came on. I cleared the code with the scan gauge but the idle was still rough after several start ups and shut downs (x3) and no code thrown or check engine light. Worried, I shut it down and came back in to the office.

Not knowing what to do, I searched here for the code after checking the scan gauge, then went on line for more details seeing as not much came up for the code here. While waiting for a response to this thread and thinking about the possibility of the problem being caused by carbon build up in the EGR, I decided to try an old trick that used to work on my ex girl friends old 75 Buick Apollo (don't laugh!).

So I go outside, grab a screw driver from the glove box, open the hood and start looking around the EGR valve. I decided to first disconnect and reconnect plug going in to the top of the EGR. I then used the screw driver and started tapping (lightly) on the EGR and all pipes leading to it. I then got in the VX, started it up and the idle was perfect, no check engine light and all seemed OK.

I went ahead and grabbed a coffee, came back to work and all is well now. I don't suspect this resolved the problem entirely but it seems to be working fine for right now. That rough idle was killing me, and I really didn't want to drive it because I'm sure an idle like that can't be good for something!

I need to take the VX in to have the 75,000 mile service done soon so I'll make sure they look in to the EGR's condition at that time :)

But for now, all is well and is something to try if this happens to you some day :)

You likely have a sticking EGR, which you momentarily "freed" with the screwdriver tapping. As Tone mentions cleaning the EGR and tube of carbon deposits will help, for a while. Excessive deposit build-up is a sign of a sticking or intermittent EGR problem. Unfortunately, this is more indicative of the design and is very common among a wide-range of EGR designs in use on passenger vehicles. More and more new EGR valves are touting "non-stick" designs, so maybe there's one out there that can be retro-fitted to our V6.

It'd be nice if we could each have one of these in the tool chest: EGR Tester But at $250 a pop it's a pricy tool for an occasional problem. :p

For those interested in what the EGR system is and why you don't necessarily want to bypass it, here's a pretty decent article: Understanding EGR Systems.

Does this solved your problem? I know it's been a while, but I have the same symptons on my RPM's and a P0401 code (low or insufficient EGR flow). First time I replace the EGR Valve, and the problem returns. Next, I clean everything with choke cleaner and even with brake cleaner and nothing. I also perform the Sea Foam treatment and was a waste of time. Doing some search, I found on the net something about the "DPFE", do we have one on our Vx's? And where is it? Next thing I'm gonna try is the "For Sale" sign. please let me know. Thanks, Axel Ironman Vx 1999

i got the same po401 code that comes on daily.
i have replaced the map sensor,egr valve,and made sure the pipe running from the egr to the exhaust manifold was clear..that is everything the manual sates to do.
still get the code every day several times a day
if you get this fixed let me know how you did it
thanx
ken