Hello again forum.

My 99 PA (3.8 L) dropped an SES light and code a while back. Read the code, P0401 EGR insufficent flow. Tried to clean both tubes under the valve with brake fluid and a nylon tie wrap (twisting down). Code returned and I thought it may be in the valve. Bought a new EGR valve, installed it then cleared codes. A few days later the P0401 code was back. Can't believe it'* the EGR valve. Reset code one more time, but back today.

What can I do to allow sufficent flow for the valve? The two tubes below the EGR are different sizes and I don't know which one is the problem. What is the fix, short of taking it in to a dealership? I tried the 'run the engine with the EGR removed' trick but didn't help. HELP!!

Read this:

https://www.gmforum.com/obd-ii-trouble-shooting-153/p0401-284082/

Sounds like you might have a cracked EGR tube.

Is the EGR tube the smaller (silver colored) tube below the EGR valve? If so is it difficult to remove for cleaning? Is there a cleaning method if tube is left in place? Thanks.

I agree, sounds like a cracked tube. Only way to check is to remove it and hold it up to a light. The tube that is likely cracked is the one from the valve to the LIM under the throttle body.

Eddie, we don't think this something that can be corrected by cleaning. The tube is likely cracked and needs to be replaced if it is.

After watching the service engine soon light for some time now (code 0401) I tackled the EGR to intake manifold tube. A little tough to remove but can be done. It was open and not cracked so I sprayed a small amount of carb cleaner in the intake hole, repalced tube.
Now comes my question this time. First it starts and idles great. Problem (if it is one) it won't accelerate above 4000 RPM. At 4K rpm it will bounce up and down a few hundred rpm'*. I'm keeping in mind it'* still in open loop. May go above 4K rpm after closed loop. Yes, no, maybe??
Next associated question. At first I thought I wouild need to remove the throttle body to have access to the EGR tube. Started by backing the body retaining bolt out and saw it was dripping coolant (antifreeze) below the throttle body. Noticed a slight damp area from what seemed to be an old seepage. I'v noticed a faint antifreeze smell for weeks now. Begining to wonder if the seepage and 0401 code is associated. Don't sound right. Did notice the throttle body was warped a bit from top to bottom. There should have been more bolts engineered around this area. My opinion.
I had replaced earlier (month or so ago) the EGR valve and the SES light stayed off for a week or so. Thought I had it.
Back to the fluctuating RPM issue. Any opinions? Tips? Ridicule?

Thanks guy'*. Eddie

Hoping I would get a response from this post. Thanks in advance.
PS - SES light came back on - uggg.

Is your coolant level dropping at all? Do you smell coolant in the exhaust (sweet smell)? Check the oil dip stick and the bottom of the oil filler cap for anything unusual. If you changed the oil lately, was if foamy?

I have the same problem P0401. Still working on solving this issue after many problems, this is the last one. My EGR reads .670v at idle on the pintle position signal(pin C). It shouldn't read anything, because it should be closed at idle. This would cause the code to set because the pcm is going off that as it'* base.
The car has a rev limit in park which is 4k rpm.

You shouldn't jump on a 5 year old post....should start your own.....

At Idle the EGR valve should be closed......if the pintle position sensor is indicating it is open, then the EGR has to be replaced.....

Usually, a scan tool will read % rather than voltage.......so at idle or even with the engine off, key on, scan data should read 0%.......I think back probing the feedback signal, should be between 0 and 1.0 volts if I remember right.....so .67 means it is more than halfway open(if the EGR was actually half open at Idle, it would stumble and die).......so it is the pintle position sensor that is at fault, and can only be fixed with a new EGR......

Basically, the test the PCM runs is, while the vehicle is cruising, it will command the EGR open, and look for a corresponding change in the MAP output....if it doesn't see one, the code is set....