can a decat thats not mapped cause fault code p0171 too lean? and high ltft

[arronleeds]

I have found a mk2 cupra r i really like, however the owner says that he put a decat on it and didnt get it mapped, every so many miles it will throw an eml and give out a p0171 fault code stating bank 1 is too lean. He has shown me the long term fuel trims when the fault occurs and it is +23% which is high. can this be due to the car no longer having a catalyst?

 

[R3k1355]

Possibly, but could be other issues too.

Not a great look if someone is doing a half-assed job modifying a car.

 

[martin j.]

Might need a spacer on the decat to fool the sensor?

 

[arronleeds]

turns out it was either the maf sensor or the ramair intake.