CODE P0401

1999 Saturn SL2



May, 5, 2010 AT 12:29 PM

Computer problem
1999 Saturn SL2 4 cyl Front Wheel Drive Automatic 180, 00 miles

Okay here goes. I have a 1999 Saturn SL2. I got the infamous P0401 engine code, which means which is for EGR insufficient flow.

Okay Here are the things that have been taken care of in the last year emission wise:

1. New catalytic converter
2. New 02 sensor, front one.
3. New Engine Coolant Temperture Sensor
4. New EGR valve, gasket
5. New PCV valve
6. New correctly gapped NGK spark plugs
7. New Plug wires
8. EGR passages checked for flow and cleaned as well as can be without taking exhaust manifold off.

Car's oil usage is about a quart every 900 miles or so.

So the question is, is there any other sensor or test I can conduct that might contribute to this issue and ultimately have it solved?


6 Answers



May, 6, 2010 AT 4:39 AM


May, 6, 2010 AT 12:51 PM

First of all thank u so much for ur donation. What I would try first unless u have already tried this is to remove the egr valve then Start the car if the car idles normal like the egr valve was still on then u have a plugged egr port. If the rpm only goes up a little then u have a restricted egr port. If the rpm goes up fast and it's really noisey then ur port is clear. Before I change every egr I do this to help clear out any loose carbon that might make the new valve stick and to make sure that egr port is not clogged or retricted. Also it's ok to reuse that egr valve gasket I reuse them all the time if I suspect a sticky valve or restricted port. Let me know what u find.



May, 6, 2010 AT 5:26 PM

So when I took the EGR valve off (it is a brand new valve btw), a ton of junk blew out of one of the egr port. I noticed that one of the ports sucks in and the other blows out exhaust. I assume that is how it is supposed to function.

Yes it is noiser, but I don't think the idle was faster, so I suspect we might have a plugged EGR exhaust port.

What is the recommended procedure to clear this out if it is truly clogged? I suspect the exhaust manifold will have to come off and that is probably where the problem child is. What is most likely the culprit?



May, 6, 2010 AT 6:27 PM

Yeah u have exhaust and vaccum on the ports one goes to the intake manifold the other goes exhaust manifold. Egr is short for exhaust gas recirculation. With the egr valve off and idling the rpms should have went up alot from the vaccuum leak if it stayed the same u have a blocked vaccuum port to ur intake manifold. If it was noisey and alot of stuff blew out that means ur exhaust port is ok. What happens is when ur egr valve opens it lets exhaust gases into ur intake manifold port unfornatley it also allows carbon from ur exhaust to enter that intake port going into ur intake manifold then eventually it becomes blocked causing ur code for egr flow. So ur going to have to clean out the port that sucks and doesnt blow. Un can try doing without taking off ur intake manifold which I suggest. Remove ur egr valve get some good stuff that eats carbon up like a carbon cleaner and put that in the intake port under egr valve let it soak for like 30 mins or so the longer better.U can try using some stiff bailing wire to clear also u could get a old spedometer cable cut a short piece of it fry the end put it in a cordless drill with the drill in reverse and use that like a mini hone to help clear it out also still using the stiff bailing wire for the hard pieces of carbon. If that doesnt work then u would have to remove the intake to acess better to port. But the clog is usually closer to part of where the exhaust comes in. Try clearing it without taking the intake manifold like I said if that doesnt work then check back in with me.



May, 6, 2010 AT 8:31 PM

So what I plan on doing is to take it off and get a good carbon cleaner and let it soak for a couple of hours. That and some manual cleaning as you suggest.

It probably is partially clogged because the SES light will not go on until I let off the throttle after the car has been driven on the freeway. It won't do it everytime, but it seems to take at least a good sized trip to trip it.



May, 6, 2010 AT 9:20 PM

Sounds like a plan yeah if ur egr valve is off and ur car is idling and not racing u have a clog let me know hoe it comes out.

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