Good morning,

I am new to the forum and hope someone can help me.

I have a 1999 Saturn SL2 SOHC with 258,000 miles. I am in the process of getting it inspected and have the dreaded P0401 code. I had replaced the EGR last year so I removed the EGR Valve and tried to clean the ports on the intake several times. This did not work so I removed the intake manifold this past weekend and did a thorough cleaning. Also replaced the Intake Manifold Gasket. The code still came on so I took it to a mechanic to have it scanned again. He said the EGR Feedback sensor was sending false codes to the system, so I went and got another EGR valve and installed last night.

I had a mechanic reset the code this morning and after I drove about 35 miles, the light came on again. Took it to O'Reillys and the same code is on.

Can anyone please help? I have also replaced the Throttle Position Sensor and the Idle Control Sensor in the past 3 months.

Thanks,

Brian

 

Unfortunately, many of the computerized error codes that get flagged in todays modern and yes 1999 is more modern than a 15 year old car used to be, car involve a right fair amount of complexity. Being able to fix things simply has been lost in order to get things that require repairs infrequently. And have all of the whiz bang features that now make a car more of an appliance than not.
So addressing your question directly here is the repair procedure called out in my Saturn Diagnostic set of 18 CD's I have that cover automotive service

Diagnostic Procedures
1) Install scan tool. Start engine, Using Scan Tool, command EGR valve to full open. If engine begins to run rough when EGR is opened, problem is intermittent. See Diagnostic Aids. If engine does not run rough when EGR is opened, go to next step.
2) If EGR pintle position increases when valve is opened,clean or replace EGR valve. If EGR pintle position does not increase when valve is opened, refer to DTC P0404 test for Diagnosis.

Diagnostic Aids.
When attempting to diagnose an intermittent problem, use scan tool to review malfunction history information. "Tis data can be used to duplicate a problem.
Scan Tool can read the number of deceleration tests that have been performed since the DTCs were cleared. It can also display the EGR decel average value as well as the fail threshold when DTC was set. he average must be greater than the threshold to set DTC.
Battery voltage is supplied to EGR valve terminal "E" with ignition on. Carbon build-up around pintle valve may restrict exhaust gas flow. Diagnose other DTC's first, especially MAP DTC, before diagnosing DTC 0401

This seems to say that the egr function has some problems with carbon build up that causes mechanical problems with the movement of some of it's parts.
And those parts are commanded to move electronically and there is a feed back signal that says it actually moved. There also seems to be a relationship with the MAP sensor in that flow restrictions are diagnosed during deceleration and a change in the MAP sensor is expected, and if the MAP sensor change is not with in it expected range during deceleration, a restricted flow is assumed.
So at least one obscure relationship might very well be a defective MAP sensor.


I hope some where in here there is some help. I have the capability of printing things out, but then I have to type stuff out to send it off to some one else.
Good luck.