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Discussion Starter #1
Hello All! I’ve became victim to the p0401 code. And I’ve searched forums for days nows. Code reads as p0401 EGR flow insufficient. Car runs and drives completely fine no hesitation or anything. Idles perfectly.

I removed the egr valve 1 vac line,2 bolts,& 2 coolant hoses. Cleaned egr, cleaned intake port, and cleaned gasket. Performed a vacuum test on the egr and it held vacuum. Then added fluid to one side of the chamber and it didn’t leak through, pulled a vacuum which moved the diaphragm inside and the fluid leaked into the other chamber. Conclusion is that the egr valve itself is fine.

Now removed the the egr solenoid 2 bolts, 2 vac lines, 1 connector. Performed another vacuum test. Without power to the solenoid it leaked down. Added power and it held a vacuum. So now the solenoid is fine.

Removed throttle body noticed the gasket was in fact on wrong. It was flipped to the wrong side. Also covered in gasket sealant. The sealant had a noticeable indention on the gasket for the chambers E & A indicated on top of the TB. The chambers run to vacuum lines on top of the TB. Wonder if the sealant clogged part of the ports for E & A had was causing insufficient flow?? Cleaned the TB and intake and replaced TB gasket.

I done all of this within the day and drove the car for roughly 20 miles and no light. I had the battery disconnected so I’m assuming it’s now through the drive cycle. Hooked my scanner up and the code is under pending. (I didn’t clear the code before or after repairs) Was reading about a resistor inside a white dashed vac line? Could anyone pin point location? And location of a vacuum controller? Hopefully it will pass emissions come Monday morning I’ll update soon.
 

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It sure sounds like you may not be getting vacuum to the parts if the port is clogged, it's also possible the EGR passage into the manifold is clogged with carbon, did you check that it's clear when you had the valve off? You can connect a vacuum gauge to the port and run the engine and rev it up and down to see the vacuum change with throttle and engine speed.
 

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Discussion Starter #3
Yes I scrubbed the intake port with a fine bristle brush and some cleaner. Where should I hook the gauge up too for the vacuum lines? At the T-Joint or ontop the TB? Also do you know where that little resistor piece is inside the vacuum lines?

And yes the light came back on
 

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Discussion Starter #5
Found the diagram. Never mind.
Also I removed the MAP sensor and noticed it was also gummed with gasket sealer. Is there suppose to be a gasket for the MAP. I’m going to spray carb cleaner around checking for a vacuum leak. But there’s no stumble or hesitation at all. Car runs great.
 

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Check for vacuum at the port on the engine and then check it at the solenoid and then check it at the valve itself (which may need you to drive the car while watching the gauge stuck to the hood)
 

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Discussion Starter #7
UPDATE:

After cleaning and checking the egr valve,solenoid,& intake ports. I jumped to the repair manual and done the egr system check at cold engine temps. It remained at zero vacuum. (Which it should) I did not preform the egr system check at warm engine temps nor did I check the egr valve with warm engine temps. (I’ll do them in the morning) I checked the vacuum control valve and it read into spec at idle it was roughly 23.0 kPa. (Manual says it should be roughly 21.3-24.0).

During this process I decided to remove the line that runs from the control valve to a “tee” that plugs into the egr valve and solenoid. I cleaned the 2 lines that “tee” off and cleaned the main line. No fluid would come out of the main line and I could not blow through it. This line is also the one with the restrictor inside of it. (Removed restrictior, cleaned,& reinstalled)

Lastly I done the egr vacuum port test which made me plug into the top of th TB and it climbed up to 20 Hg. Reset vacuum pump and it took one sec to climb back up to 20 Hg.

None of the tests performed failed only problem was the clogged main line. Hopefully that was my issue. Checked for vacuum leaks while car was running and nothing came about. Reset codes and I’ll update by Monday!
 

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Discussion Starter #8
Welp.. On my way to work this morning my light came on. Bank 1 system to lean. When I unplugged the vacuum line on top of the tb I had to start the car. And mistakenly hooked the hand pump to the vac-line instead of the tb nipple. Could this have thrown the code? I’m going to reassure a plugged all the vac lines back up tonight. Could me removing the small resister cause this all? Read on other posts that it fixed their issue. P0401 has not popped a code either.
 

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Discussion Starter #9
Checked tonight for any vac lines unplugged. Nothing is disconnected. Re checked everything. Cleaned and reinstalled resister. Turned light off AGAIN.
 

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:yesway: Nice job. I've been driving around for over a month with the CEL on because of this same code :lol: Been lazy to work on the car.
 

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Discussion Starter #12
SAME! Tags were due and my state has emission laws. CEL equals an automatic fail. It’s more then likely that vacuum line running for the vacuum controller to the “tee fitting” that resister has a small pin hole in it that gets clogged. Easy to get to also. Reached my hand down by the alternator and just felt around.
 

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Bumping this thread because I'm having the same P0401 issue. I have a 2003 Eclipse Spyder GT 3.0L v6 with variable induction and I've been testing all my components but I noticed there is no vacuum being supplied by the throttle nipples, both A and E. Does anyone know what the vacuum specs on these is supposed to be? And if they are supposed to be supplying vacuum constantly or at certain periods?
 
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