P0170 code

[AndyR]

Hi all, looking for help regarding my daughters boyfriends Zafira 1.8 Elegance. 

It has had a fault code come up, P0170, fuel trim malfunction.  On doing some research, I found that it's a mixture problem. Either too rich, or to lean. What is needed to cure this problem please. Its very erratic on tick over, and  when you rev it, the revs are slow to die down. 

Could the code be the cause. Any advice would be much appreciated.  I'm more Astra than zafira.  But the owner knows even less.

TIA  Andy. 

[AndyR]

An update on this fault. It turns out that both O2 sensors needed replacing. Car had a full system check, and only fault that could be found was Lambda sensors (o2). So 2 new ones purchased and now been fitted. 

[AndyR]

An update on the update.

The Zafira is now back doing what it was doing before I replaced bothO2 sensors. Revs are up and down. And when changing gear, it sounds like you're slipping the clutch because the revs are still high, and not dropping off like they're supposed to. 

Could this be the maf sensor, or even the throttle body playing up?

Any pointers in the right direction would be much appreciated, Thanks in advance.

AndyR.