2004 Volvo V40 P0171 Code LTFT 17.2

P0171

Lean fuel condition could be caused by one of the following below:

1. Vacuum leaks
2. EGR and PCV valve.
3. Low fuel pressure.
4. Dirty fuel injectors.
5. Mass Air Flow Sensor.
6. Oxygen Sensor.

Do you have a howling noise with the check engine light on? If you do, then you have an internal vacuum leak in the oil trap box. You may still be covered by an extended emissions warranty of 10 years/150k miles to get it replaced at no charge. If that is ok, make sure oil cap is properly secured and oil dipstick is properly secured as well. If left loose, this will cause fuel trim problems as well. Inspect for any leaks and pay close attention to the pcv hose that is on the oil trap. The oil trap is the oil filter housing. Remove air snorkel from air box like you would to access oil filter. You will see a hose that attaches to the box and goes up to the cam cover. That hose gets brittle and breaks causing an intake leak. They also tear in between the plastic intake and cam cover but you would need to remove the plastic intake off to inspect. If that hose is damaged, replace it and unplugg the engine control module connectors on the side of the air box to reset fuel trim adaptations. If all that is good, you have a dirty throttle body and you will need to remove it to clean it. Once you clean it, unplug the ecm connectors to reset fuel trim adaptations for this repair as well. After you clean it, take it in to Volvo to see if there is an available software update for the ECM. If there is one, have it done. This will recalibrate the mass air flow sensor and reduce the number of adaptations it sees so it will not be so sensitive and trigger the light from coming on. Also does not hurt to ask if the software will be covered by the extended EMS software warranty which is also 10 years/150k miles but that is not always the case? Just let them know you did some repairs and you wanted to have the ECM software updated. Good luck and let me know what you find.