lean code

[Jurassicspark]

P0171 code keeps appearing on my Zafira. It appears when I drive over 25 mph, and the short and long-term fuel trims increase while driving. The short trim would be on 15 percent and the long trim on 0%. Sometimes the short trim returns to 0 and the long trim increases gradually to 18%. I tried ruling out it being a vacuum leak by pressing the acc pedal and seeing if the fuel trims would jump down, but it did not affect anything.



The code came yesterday, I cleared it, and it returned again today. Some help on this, please.

 

[carmanmemoranda]

02 sensor maybe ?

Exhaust emissions figures would be a good start

 

[Jurassicspark]

02 sensor maybe ?

Any valid tests for the o2 sensor? It is fluctuating from 0 to 1v..

 

[Jurassicspark]

Would blocked egr channels cause a lean code? If so, how exactly?

 

[carmanmemoranda]

I'd suggest exhaust emissions before going any further.

Emissions will show any overfuelling or underfuelling

 

[Jurassicspark]

Okay, LTFT creeps to 18% on idle, and increasing the rpm to 2k makes it reduce to 0%. It looks like its a vacuum leak somewhere. However, the short trim goes from 0% to 10% while the long trim drops...what does this indicate??