What causes the fault code P0171 (system too lean)?

Looked at the exhaust manifold and one of the studs has snapped off. Finally got a friend of a friend to take a look with tech2 clobber. Also found a pcv hose with a split.

knackeredfrontera
November 2010

I Have an astra 54 plate H and I am getting p0171 system too lean what can be cause of this?

Gary
May 2010

Thankyou for your post. I understand this is seperate from the sender unit for the temp. guage, however I am confused, how would this affect fuel mixture and produce the fault code? I was thinking it may be more like a lambda sensor, or is it that the ECU is running the engine in an emergency mode which is why the over-rich fuel mix?

knackeredfrontera
May 2010

Have you checked the engine coolant sensor , it could be out of range or the electrical connector on it might be corroded or dirty

John
May 2010