well here is another one of these threads lol
Last edited:
In need of some OBD diagnosis help.. P0171 and P0401
- Thread starter 40thSagePearl
- Start date
-
- Tags
- egr modulator mpg p0171 p0401
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
NLXTACY
Wits' End
Nearly every 401 I've dealt with has been a bad vacuum hose issue. Check all the hoses under the intake AND the brake booster hose first and replace as necessary before driving yourself nuts and spending unneeded money on other stuff. It's also a great process of elimination.
- Thread starter
- #3
Will mention this to my Mechanic as well. I did check the hoses that connect the EGR Valve and modulator which seem to be brand new. Will check the others on Friday when she goes into the shop.
I'm going to guess you have an exhaust leak upstream of the front O2 sensor. That will cause the ECU to make the engine run rich and eventually throw the P0171 code. P0401 is an egr code and there is plenty already written about that bastid.
- Thread starter
- #5
Checked both o2's on scanner... Fluctuation at idle is somewhat a bit of a misunderstanding to me as Im learning how to use the scan tool as well. It fluctuates around 0.500 in O2B1S1 (V) then will drop to 0.130 and go back up to lets say 0.700.. Same goes for the O2B1S2.. I also Cleaned the MAF with CRC MAF cleaner and at idle its about 3.85-4.00(g/s) ( not sure if thats where its supposed to be )
NLXTACY
Wits' End
Have you give through the vacuum hoses? Checked for cracks in the exhaust? Even tiny cracks.
Check for a crack in the "Y" section of the front pipe. Everything is pointing to an exhaust leak.
- Thread starter
- #8
is there a diagram of vacuum hoses ? I do know that the little plastic tab that keeps the MAF harness plugged into the MAF sensor female portion is broken off but it still fits on snug and isnt loose.. I receive readings from my MAF still so I believe it is working.
- Thread starter
- #9
will do, does the P0401 EGR code also relate to this ? I know the Modulator and EGR valve itself have already been replaced by PO with a good amount of new Vacuum hoses being replaced within that vicinity of those two pieces
P0401 is a completely separate issue completely separate system.
