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Old 11-21-2017, 12:53 PM   #1
zoman1719
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Default P0401 problem can't get rid of it. Tried everything.

Just wondering if anyone has experienced this with a 2002 Saturn Sl1. Keep getting code P0401. I've gotten a new EGR, cleaned all ports going to the EGR. Cleaned both intake ports, and the exhaust port through the head with the plumbing snake on a drill trick. I've sprayed the carb cleaner down and let it soak. Blown it all out with air through every port I cleaned. Even started it with the EGR off to let it force out the exhaust port of any loose carbon. I totally cleaned the exhaust manifold of carbon as well. Without the EGR on I get a lot of exhaust pressure out of the port and the intake has great suction as well. I'm now lost as to what to do. After clearing the code each time it'll come back on after about 15 minutes of highway driving. Just looking for more advice or avenues to take. Thanks.

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Old 11-21-2017, 01:18 PM   #2
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Default Re: P0401 problem can't get rid of it. Tried everything.

1-After cleaning out passages and running the engine without the egr valve in place, does the engine rev up and bounce off programmed rev limits (4k or 4.5k rpm)? When the engine reaches rev limits, this indicates the intake passage is free of exhaust build up. The exhaust passage should be free of blockage too since it feeds exhaust gases into the intake manifold for emissions purposes.

2-If the engine runs as above, the error code definition also points to either a voltage or faulty egr valve (worn out).

Cleaning the egr valve of carbon deposits should allow the pintle valve to slide open and close with its drive motor the only restriction to free movement. Worse case is replacing it altogether with an OEM one or maybe junk yard part. Other sensors that may trigger this error code may be a faulty map sensor.

The egr valve is opened during acceleration and cruise, off at idle and wide open throttle. The O2 sensor detects exhaust gases along with feedback signals from the egr valve along with other sensors the pcm determines whether or not the egr valve is opening correctly.

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Old 11-21-2017, 01:45 PM   #3
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Default Re: P0401 problem can't get rid of it. Tried everything.

The PCM reads EGR flow via the MAP sensor...if that's wonky you can end up with P0401. Should read 1-1.5v at idle on the MAP sensor, and verify the port to it in the head is clear.

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Old 11-21-2017, 02:58 PM   #4
zoman1719
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Default Re: P0401 problem can't get rid of it. Tried everything.

Quote:
Originally Posted by fdryer View Post
1-After cleaning out passages and running the engine without the egr valve in place, does the engine rev up and bounce off programmed rev limits (4k or 4.5k rpm)? When the engine reaches rev limits, this indicates the intake passage is free of exhaust build up. The exhaust passage should be free of blockage too since it feeds exhaust gases into the intake manifold for emissions purposes.

2-If the engine runs as above, the error code definition also points to either a voltage or faulty egr valve (worn out).

Cleaning the egr valve of carbon deposits should allow the pintle valve to slide open and close with its drive motor the only restriction to free movement. Worse case is replacing it altogether with an OEM one or maybe junk yard part. Other sensors that may trigger this error code may be a faulty map sensor.

The egr valve is opened during acceleration and cruise, off at idle and wide open throttle. The O2 sensor detects exhaust gases along with feedback signals from the egr valve along with other sensors the pcm determines whether or not the egr valve is opening correctly.
I will check on the MAP sensor voltage later to see what I get like you said. The EGR moves freely as I've cleaned it 100 times and is about a month old if that. And yes without the EGR and starting the car, it does immediately rev up to about 4200 RPM without hesitation.

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Old 11-21-2017, 03:58 PM   #5
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Default Re: P0401 problem can't get rid of it. Tried everything.

Keep in mind that not all replacement egr valves are alike. A few here found issues with replacements not correcting the error code and found only the OEM egr valve works. Whether or not the aftermarket manufacturers are meeting specs or not is open to debate as there are many things that goes into making egr valves work in each engine. I'm aware that prices are all over the place and that tends to sway people one way or the other. My experience with expensive parts was when two of four O2 sensors failed (heaters) less than a year apart. I saw varying prices and decided to stay with OEM (Bosch) and they are not cheap. It was either pay now or risk repeating with less expensive ones. My L300 uses wide band Lambda sensors according to service manuals. The tuners are using these for watching their air/fuel ratios on a display while most vehicles shifted to these wide band sensors as EFI systems evolve for better emissions control and overall engine performance. They were $95 a piece.

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