yesterday we had a lot of freezing rain and snow here in Texas. i had ran out of beer in the man cave and had to go to store and get some. i thought this would be a great chance for me to check out my 4x4 in this truck i bought a few weeks ago. i had already done a lot of stuff to fix the 7 codes that the truck had when i bought it. for the last couple of days i had 0 codes coming up on my reader. so before leaving to go to store i switched on the 4H. made it to the store no problem. on the way home i had my service engine soon light come on. so when i got home, i plugged in my reader and got 2 codes, 171 and 174. would running in 4x4 throw the codes while 2wd doesnt? any help on this would be greatly appreciated. i was thinking maybe i have a vacuum leak somewhere, but dont understand why in 4x4. thanks in advance for any help, because i am just trying my best to get this truck back to where it should be. the person who had this truck before does not ever need to own another vehicle with the way this truck was neglected.

 

It's just a coincidence this happened when you were in 4hi. Don't let that make you assume that was the culprit. The codes you stated are as follows:

P0171 System Adaptive fuel too lean (Bank 1)
P0172 System Adaptive fuel too rich (Bank 1)
P0174 System Adaptive fuel too lean (Bank 2)
P0175 System Adaptive fuel too rich (Bank 2)

These codes can be caused by a plethora of different things and is in now way directly related to the 4wd system.

I would start by checking the simple stuff; PCV valve and hose, Plugs, COPS, and other ignition related things.

 

The worst case scenario would be a bad intake manifold gasket.

 

thanks for the info. i have already checked PCV, all is good there. very strong suction on the valve. i have changed out all the plugs, and after doing that i still had 3 codes that came up, P1131, P0171, and P0305. i changed out the COP on cylinder #5, and all 3 of the codes were gone. i thought maybe that replacing that COP had fixed my problem until yesterday when i switched to 4wd. how do i check if the intake manifold gasket is bad?

 

Spray around it with some wd-40 or a mixture of something with a tad bit of soap to check for air.

 

Ok I will give that a try whenever it thaws out a little. Thanks for the tip