P0401 LOW EGR FLOW... NOT CAUSED BY THE OBVIOUS... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-20-2005, 01:58 AM   #1
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Default P0401 LOW EGR FLOW... NOT CAUSED BY THE OBVIOUS...

yeah, i finally solved the problem with the P0401 CODE on my 97 bonneville 3800 vin K

believe it or not, it was caused by the repair shop leaving the PCV valve out when they changed the upper plenum...

it sits directly below the MAP sensor... they swapped the plenum and left the PCV valve in the old part... it caused the code to set...

i found out, that code is more about the MAP SENSOR'* ability to sense pressure change in the intake manifold when the egr valve is commanded on by the computer, than whether egr gasses are flowing or not...

since the pcv valve was missing, the MAP SENSOR was sensing no change in the intake manifold pressure, which told it the egr wasn't flowing... but it was really the fact that the PCV VALVE wasnt allowing the manifold pressure to build to a point that it could drop when the egr opened.... this in turn sent a false signal to the MAP SENSOR...

all over a missing PCV VALVE...
now a faulty one, (sticking open) could cause the same problem....

hope this helps you...

check or replace the PCV VALVE cheap insurance for less than $5 bucks..

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Old 04-20-2005, 02:10 AM   #2
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Good Job!!!!
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Old 04-20-2005, 03:07 AM   #3
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Cam, repeatedly posting exactly the same text in several topics clutters the database. It also can be confusing for members that don't have the same problem as you. A missing PCV valve is extremely rare. Please stop posting the same text over and over, and please stop digging up topics from 2003.
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