My 2000 buick lesabre is running and idling great, but the check engine light stays on.


Asked by Jul 05, 2017 at 06:09 PM about the 2000 Buick LeSabre Custom Sedan FWD

Question type: Maintenance & Repair

Recent mtce: replaced plugs, coil packs and ignition module (p0301), coolant elbows to heater, upper intake manifold (coolant and air leaks) (p0401), map sensor (broke the old one removing it), and the engine now idles good and runs good. If I disconnect the maf sensor it idles rough or stalls. After clearing the codes and running about 20 miles the check engine light came on again (p0401).  Now I can clear the code with the code reader, but the light will not turn off.

11 Answers


P0401 is a code for insufficient egr flow. The egr is near the throttle body It looks like a canister with a black plastic top with a 4 wire connector going to it. There is also a metal pipe that goes to the exhaust manifold connected to it. These buicks have problems with the passage in the intake manifold plugging up with soot and carbon. You should remove the egr and check that both passages are clear. I use a piece of wire like a coathanger to check for blockages. You will need to remove the throttle body and place something near the opening of the passage to catch the bits of carbon you will break free.

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I forgot to mention that I replaced the EGR valve and cleaned the throttle body and at the EGR the pipe looked clear. But i did not poke anything through the pipe. I'll give that a try and let you know the results.


The passage in the intake manifold under the egr valve is the most important one to check One passage goes to the pipe the other feeds exhaust gasses into the intake when the valve opens. This is the passage that causes egr no flow low flow codes. It gets filled with crud.

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Thanks. Cant get to it til this afternoon, but I'll give it a try then. The sleeve that the manifold sits on was blackened, but appeared to be open. I had poked a screwdriver into it and didn't encounter any blockage, but I haven't poked anything all the way through so it's still a possibility.


Tried it and could not find anything to make the bends, but I connected my compressor to it and blew out a little dust. There was plenty of air flow through it. However, when I put the throttle body back I noticed a crack in the air line connector. I saw it before (closed) and it looked like a mold line from making the connector. I connected it, the crack opened. I taped it, cleared the code, ran the engine and no light. Thanks again.

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Oooops. Still runs fine, but at interstate speeds the check engine light came back on (p0401 again).


That passage is very hard to clean. If the passage is clean, squeaky clean. Then the problem will be a bad egr.


There are two passages. You need to remove the egr from the intake to get to them. One goes to the metal tube and the other goes to the inside of the intake manifold. The one that feeds the intake is the one that plugs up. I just want to make sure you have done everything you can do before replacing the egr.

I'm having that same problem. With the check engine light coming on even though the car runs great. It has recently had new spark plugs and wires. New hoses and below and coolants


Sorry to hear that Martin. The problem can be anything to do with the EGR floe or the vacuum. I didn't have any vacuum codes, but I found a leak where the EVAP and fuel pressure vacuum hoses connect to the throttle body. I replaced the harness and it cleared the Check Engine Light. Then it came back on with a P0401 code again. I suspect a sticking EVAP purge solenoid. Without ebay, I couldn't afford these replacements. Code reader $15 on ebay.


Replaced EVAP purge solenoid 7/20/17 and check engine light turned off. The question now is for how long.

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