What causes the fault code P0171 (system too lean). The car is a Vauxhall Frontera B series with the x22se engine and is a 1999 model. I have put a new MAP sensor in but the code is still coming up. It uses a hell of a lot of fuel and the plugs are sooty as is the exhaust smoke. No overheating and it idles fairly well.

Knackeredfrontera, May 2010

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