Service Engine Soon - Insufficient EGR flow

I have a 1997 Pontiac Grand Prix 3.8. The Service Engine Soon light came on. Took to local auto parts store. Codes read Insufficient EGR flow. Took EGR valve off. Cleaned it and the tube to it really well. It had a lot of carbon. Now it is clean as new (took me a while). Light is still on. How long will it take for the cycle to check this and reset the light if everything is ok? If the light does not reset what could it be? I have heard that the GM EGR valves rarely actually go bad. Thanks.

What was the DTC error code? Most EGR codes must be reset with a scanner and very seldom correct over a few drive cycles.

If it is P0401 check out the PCV valve. You may have a bad or missing o-ring seal (small black one). It will affect MAP vacuum which is used to perform the EGR flow test.

Did you recently replace the PCV valve?

Did you replace the gasket when you cleaned the EGR? My code wouldn't clear until I replaced the gasket. As well as I remember I think my gasket had a crack in it.

I replaced the PCV valve a week ago. I did use the oring off the old PCV valve because it looked good. Do I need to replace the oring with a new one? Is the oring something that any auto parts store should have?

I did not replace the gasket on the EGR valve. How hard was it to get the old gasket off? Where did you get a new gasket and how much did it cost?

Thanks

Do you recall the specific error code. It would be helpful. New o-rings should be installed. Also make sure the big orange o-ring is in place. Also that the plastic holder with the spring that holds the MAP sensor is good and tight over the EGR valve.

O-rings are available at all auto parts stores.

Did you have any EGR codes before the PCV valve work?

I think the code was P0401, Insufficient EGR flow.

Now that you mentioned it, I only got that code about a week after replacing the PCV valve. Do I just need to call my local auto parts store and tell them I need the orings for my PCV valve and the gasket for my EGR valve? How expensive do you think all that would be?

Thanks again for the help.

I think the code was P0401, Insufficient EGR flow.

Now that you mentioned it, I only got that code about a week after replacing the PCV valve. Do I just need to call my local auto parts store and tell them I need the orings for my PCV valve and the gasket for my EGR valve? How expensive do you think all that would be?

Thanks again for the help.

Yep, thats a classic PCV valve error code and doesn't show up until after you've done a PCV job. It is very common. However, it shows up as a EGR fault code.

The auto parts store should be able to match up the o-ring. They have bulk o-ring packets of various sizes. I've seen them at Autozone for under $5.00.

Not sure about the cost on the EGR gasket.

Also, the GM dealer has a PCV valve repair kit available for under $15.00. It has the o-rings in the kit along with the spring, etc.

After the parts are replaced you will need to have the DTC error code and SES light reset. Then run it for a few drive cycles to see if it is really fixed. Good luck!

PCV Valve Kit - AC Delco/GM part # 89017274 List is $20.06

That is great. I will pick up the orings and gasket on my way home tonight. What is the easiest way to get the old gasket off the EGR valve?

The gasket is not that difficult to remove. I used a knife and a scraper to get mine off. It is an aluminized type and costs range from about $2 to about $14 according to the brand you get. I think I paid about $5 for mine.

I checked the oring on the pcv valve. It was in good shape. I got a new gasket for the EGR valve. Had code cleared. Code came back. When looking at the map sensor on top the pcv valve, I noticed the seal on the map sensor was totally torn up.

I noticed this too.... When I attempt to take the oil cap off while the engine is running, the engine will cut off. Is this normal?

I am wondering if I need to replace the map sensor. Could that be causing my code?

I checked the oring on the pcv valve. It was in good shape. I got a new gasket for the EGR valve. Had code cleared. Code came back. When looking at the map sensor on top the pcv valve, I noticed the seal on the map sensor was totally torn up.

I noticed this too.... When I attempt to take the oil cap off while the engine is running, the engine will cut off. Is this normal?

I am wondering if I need to replace the map sensor. Could that be causing my code?

The way the PCM tests the flow of the EGR valve is by using MAP pressure and then comparing it over a short period of time. The orange accordian seal on the MAP sensor should not be damaged or you will lose the sealing capability.

On taking the oil cap off rpms should drop but the engine should not die out. I tested my GTP and Regal with Series II 3800 normally aspirated and neither cut off.

Do you still have the original upper intake manifold (plenum)? The 1997 - 1998 UIM have known problems with the EGR stovepipe getting damaged.

If the accordian seal is damaged, could this be causing the Service Engine Soon light to come on, and give me the Insufficient EGR flow code?

I have checked looked at the pipe and it appears to look ok. Could you send me a picture of exactly what you are talking about (email to [email protected]). How could the stove pipe get damaged? Just curious so I know kind of what to look for.

Thanks for the help.

If the accordian seal is damaged, could this be causing the Service Engine Soon light to come on, and give me the Insufficient EGR flow code?

I have checked looked at the pipe and it appears to look ok. Could you send me a picture of exactly what you are talking about (email to [email protected]). How could the stove pipe get damaged? Just curious so I know kind of what to look for.

Thanks for the help.

Its possible but I've seen the seal pretty bad on MAP sensors and not give any fault light/DTC error codes or cause driveability problems. Acoording to the way the circuit operates MAP pressure is used but it could even be a bad EGR valve. Is the code still P0401?

On the EGR stovepipe damage, it is internal to the UIM. The only way to tell is to remove the UIM. You cannot tell looking external. However, with this problem you may get an unexplained loss of coolant.

I will have the code checked again. The reason I did not think it was the EGR valve is because from my experience these GM EGR valves rarely go bad. I did clean the EGR valve out the carb cleaner and a snake. I have not seen (or smelled in the exhaust) any coolant loss. The motor is running fine. As I mentioned before, I just noticed an unusually high amount of vacuum. I just want to drive everything before replacing the EGR valve since it is almost $200. Again, the light (and code) only appeared after I changed the PCV valve, but that could be just coincidence.

I will have the code checked again. The reason I did not think it was the EGR valve is because from my experience these GM EGR valves rarely go bad. I did clean the EGR valve out the carb cleaner and a snake. I have not seen (or smelled in the exhaust) any coolant loss. The motor is running fine. As I mentioned before, I just noticed an unusually high amount of vacuum. I just want to drive everything before replacing the EGR valve since it is almost $200. Again, the light (and code) only appeared after I changed the PCV valve, but that could be just coincidence.

Yes, the vacuum problem is concerning. P0401 is a common problem when PCV valve work is done but normally it is caused by omission of the small black o-ring. If the MAP sensor seal is that bad I'd consider replacing it since it is a lot cheaper than the EGR valve. It is related to the PCV valve work since you have to remove it to get the the PCV. EGR valves on the SII 3800 do go bad but normally they stick open. Yours is the opposite because you are experiencing a reduction in flow. However, due to the cost I would make sure other things are not causing the problem.

My GM Mode 6 reference guide states that diagnostics will determine if there is a reduction in EGR flow. Theory of operation: With EGR valve open the peak + MAP pressure is monitored over a time of 1 second. This value is compared with a treshold from engine speed versus barometric table and the difference is computed. The result is statistically filtered and compared to a decision limit. P0401 is set when the filtered result exceeds the decision limit.

Does this theory make sense to you:

Map Sensor seal is bad so PCV valve closed not allowing proper ventilation. This creates the vacuum, which in turn does not allow the EGR valve to open, or sticks closed. Thus causing the error code.

Does this theory make sense to you:

Map Sensor seal is bad so PCV valve closed not allowing proper ventilation. This creates the vacuum, which in turn does not allow the EGR valve to open, or sticks closed. Thus causing the error code.

No it does not. The MAP sensor is just a sensor. It has nothing to do with how engine vacuum is developed or PCV valve operation. You could block off the MAP sensor hole on the plastic retainer and the engine will work fine until MAP values are required for normal engine operating conditions and diagnostics. Remove MAP sensor fron the retaining clips and put your finger over the hole. Also, the EGR valve will open or close regardless of what the MAP sensor is doing. It has its own parameters for operation. If your MAP sensor seal is that bad you should be able to hear it audibly in the form of a vacuum leak. Also the engine idle will be very erratic and engine may stall.

I just looked at the PCV valve again. The big orange oring is on there and in good condition. The black oring that actually goes around the pcv valve is completely missing. Could this cause the problems I have been having? Thanks.

As bnaylor3400 stated twice before, a missing or damaged lower black o-ring on the PCV valve WILL cause the p0401 code. Get a new lower PCV o-ring, reset the code and you should be good.

As bnaylor3400 stated twice before, a missing or damaged lower black o-ring on the PCV valve WILL cause the p0401 code. Get a new lower PCV o-ring, reset the code and you should be good.

Right on Rich!!!!!!! :bigthumb:

I know, I know, I can be thick-headed some times. I do really appreciate all the help from both of you.

No problem BIGPROFITT, that's what we're here for. Sometimes you can't see what is right in front of you, especially when you're frustrated working on your own car. You are forgiven for your brain fart moment.

If you cant figure it out and don’t wana throw high dollar parts at try ED > [email protected] great guy with cheap used OEM parts. he should have EGR valve and MAP sensor galore.

No problem BIGPROFITT, that's what we're here for. Sometimes you can't see what is right in front of you, especially when you're frustrated working on your own car. You are forgiven for your brain fart moment.


Cut him some slack Rich. If a poster wants to take 5 days fixing what amounts to a less than 30 minute fix thats no problem with me. No skin off my hide. :biggrin:

For what it's worth, I had the same code for a long time on my Grand Prix. I tried cleaning the EGR valve and replaced the EGR gasket, but nothing worked. I then took off the cover of the PCV valve to check the rings. I tapped the orange ring down a little bit since it looked like it was up too far. The next time I started my car, no check engine light! Don't know if it will work for everyone, but it's free to check it out to see if it works.

Thank you, BNaylor, I never would have checked the PCV valve if it wouldn't have been for one of your posts and I'm very grateful that you take the time to post as much as you do!