1997 Pontiac bonneville P0401 DTC Egr Flow Insufficient??????

S

SP

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#1
Hello, I am new here but would really appreciate some help. Like the topic says I have a 1997 Pontiac bonneville with a P0401 DTC Egr Flow Insufficient check engine light is on. I installed the revised upper intake plenum last summer and the car ran great until a few weeks ago, the p0401 DTC was generated. The car now runs rough and feels like it is skipping.I have heard that I should pull the egr valve off the motor and see if it is plugged aswell as the tube. Should this be my first step? I am hoping that someone else here has ran into this and will have some solid advise for me. Thank You.
 
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#2
I think that is the first thing you should do is pull it off and check for carbon buildup and check around the pintle on the valve...also check the tube....Jim
 

Gus

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#3
Rare for those to get carbon on them, but I suppose it could happen...

I would be checking the harness to the EGR...it might have a broken wire or bad connection, and isn't even working.....

This code sets on a decel, when the PCM momentarily opens it up and looks for a corresponding change in the MAP sensor....If a wire is broken, it won't even work....

Now if it is stuck open, it would cause the the idle to be rough......but if the EGR is close and not functioning, you have another problem like possibly secondary ignition....

Just for haha's , check the map sensor and PCV valve....make sure the orange o-ring is in there...
 

sunny

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#4
sp, you might think it crazy but as Gus said check your PCV system out for any leaks. First start the engine and remove the oil fill cap. See if there is any suction at the oil fill hole, if so then you have a problem with the PCV system. That problem will cause the EGR code believe it or not. You should be able to lay a dollar bill against the oil fill hole and gently pull it away if the crankcase pressure is being controlled right. If it trys to pull the dollar into the valve cover then you need to get a new PCV system from the dealer. Don't try to save money using aftermarket here. Use dealer parts.
 
S

SP

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#6
Thanks for all the replies!!! Well, I pulled the EGR off this weekend and it was clean and the pintle moves freely. I pulled out the pcv and I could blow air through both sides. I think this could be the problem as others have mentioned. I replaced it when I did the intake, it is a FRAM. I am going to get one from the GM dealer and see if it changes anything. Over the weekend, the check engine light started blinking, which I think means misfire condition. For now I will try the pcv and go on from there. Also, if the problem is fixed, will the light go off after I put some miles on it or will I have to reset it with a scan tool?

Thanks again guys!!!!!!!!!!!!!
 

jay

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#7
I have seen the small passage from the EGR mounting housing to the intake clogg up on 3.1/3.4s. Remove the EGR and use a small piece of wire to clean out the port leading to the intake. I had to pull the upper intake plenum on one 3.1 to clean it out.