P0400 Code? [Archive] - GrandAmGT.com Forum


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07-06-2006, 12:57 PM
I have a 2000 Grand Am Gt. The service engine soon light keeps coming on. My mechanic has cleared it a couple times. First I had the P0402 and now when I went back the code is P0400. I have changed the gas cap and he replaced one of the plug in's on the vacuum line, but the code has come back. Anyone have any other idea's for what to check.

07-06-2006, 05:16 PM
What exactly does the scanner say that P0400 is?? Is it a leak or a "flow" problem or even a solonoid problem. I can look all this stuff up at work, but I dont have it at home.

Mike Jung
07-06-2006, 05:35 PM
P0402 = "Exhaust Gas Recirculation Flow Excessive Detected"

P0400 = "Exhaust Gas Recirculation Flow"

from: http://www.iequus.com

07-06-2006, 06:31 PM
It says P0400 = Exhaust Gas Recirculation Flow. So aside from what we have already done or checked I am not sure where to go from there.

07-07-2006, 07:29 PM
Take the EGR off and most likely you will see that its all clogged up, and that the "plunger" is stuck. You can free it up and clean all the crrap out, but its allready been clogged once so the next time its gonna clog up even faster. To make a long story short you need a new EGR valve. I do have one question for ya?? Why would your mechanic replace the gas cap if you have an EGR code????

07-07-2006, 08:26 PM
We replaced the gas cap because he figured that was the cheapest thing to try first. Today when I went back he found the problem to be that I have a gasket leaking at the top of the engine. It is causing cylinder #5 to misfire. When he sprayed some water at it misfiring went from 2 on the scanner to 48 really fast. So far each time I have gone back the code has gone from P0402 to P0400 to P0440.
I have to take my car in on monday so he can take it all apart to fix it. I really hope it is just a gasket that needs replaced and not anything else major.
Has anyone had any experience like this?

07-08-2006, 09:47 AM
Let me know what comes of this. I still done see the point of replacing the gas cap, but whatever. Did he say what gasket needs replacing?

07-08-2006, 10:11 AM
sounds like head gasket. Missfire..carbon..back into the egr when it opens, plugin' that up and setting all the codes. good your getting it fixed by the sound of it!!

07-08-2006, 10:13 AM
I believe he said one of the intake gaskets? He also mentioned something called the plelham (not sure of the spelling) that he was checkig out. I have my fingers crossed that this solves the problem. We only changed the gas cap as the rubber seal on it looked worn, and people on here had said to try that as a first step.

07-08-2006, 12:40 PM
Yes lower intakes as we all know are sort of common on these motors..... lol If he is doing the lower intake then the plenum gasket is replaced anyway. I wouldnt think your plenum would be bad. As for the gas cap, it is a good first step if you have an evap code. I wouldnt think a head gasket unless he overheated the car. These cars dont blow head gaskets unless overheated.