Error code p0171

JamesLennox

Active Member
May 2, 2015
118
0
So engine management light came on this afternoon and I plugged into my friends code reader and error p0171 came up, which is engine running to lean
I'm boosting fine? So what could it be? Any help appreciated
 

chads77

Active Member
Mar 16, 2014
28
0
manchester
Seems a few ppl have this issues me included and no answers to the problem
I've changed all the VAC hoses pcv delete with catch can new maf plugs coil packs new n75 rear 02 sensor
Anyone else have any ideas....?
 

mty12345

Active Member
Jun 17, 2011
3,765
473
bristol
Lean is usually always extra air being sucked in through a split pipe, usually a pcv hose. If the pcv system is tight then it could be a faulty MAF or something stopping the right amount of fuel being injected. If you've got vagcom or torque for Android then have a look at your long term fuel trims and see how lean it's running.
 

JamesLennox

Active Member
May 2, 2015
118
0
What's a pcv hose and where is that l?
Also I think I maybe getting that code because I have a induction kit and a decat which doesn't have the lambda sensors plugged in so I presumed it would be that
 

Sloth31

Active Member
Jul 31, 2015
33
0
Staffordshire
i also had this,

was a split hose under the inlet manifold (caution when looking under there, oil dip stick will break)

swapped pipe and light hasn't come on since, i have also found that the car seemed to jolt when changing gear, was very hard to drive smooth under boost, changing this pipe seems to have sorted that.
 

mty12345

Active Member
Jun 17, 2011
3,765
473
bristol
Like sloth says above, PCV system runs under the inlet manifold and thats the number one place for a pipe to split and cause a lean code and general rough running,

Having the lambda sensors unplugged will also cause a lean code and that's what your code will be from! The front one is before the cat and should be plugged in. Without it the car won't be able to run properly and your fuel mixture will be miles away from where it should be!

If you're running a decat, then just fit a spacer on the rear sensor to stop it throwing a code for the cat not working properly.
 
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