I have a 2015 Volvo XC60 2.0L T5 with 45k miles and I'm getting a P0171 lean code so I replaced the mass airflow sensor and new air filter. I thought I was in the clear and then the code popped again after around 1k miles. I looked for air leaks and also carefully sprayed starting fluid around the intake...no increase in revs. I was reading online that the upstream O2 sensor could be bad.
Do you think the O2 sensor is the issue? If not, what else do you think? Thanks!!
If you are very positive that there are no air leaks, then you could try changing the upstream o2 sensor. If you have a proper scan tool, take a look at the o2 sensor voltage. It should be rapidly fluctuating around 0.9 and should not be stuck at a single voltage. If it is stuck below 0.5 volts, then it should be replaced. I would make sure you check all your vacuum lines (turbocharged engines have lots of vacuum lines) and all intake piping going into the turbo as well. Turbocharged engines also have a MAP sensor for measuring air pressure in the intake manifold and charge pipe, so check that out too. It may just need to be cleaned.
@Razmigb - thanks for the tips...I'll take another look and report back what I find.
Just an update in case someone else comes across this problem. I tired to change the upstream O2 sensor but it wouldn't budge. I ended up taking it in to a mechanic who had the tools to get it out. He confirmed it was the O2 sensor causing the lean condition. He also found the thermostat was stuck open which he said could throw a code. So far so good...hopefully I'm fixed and good to go.