My Check Engine light came on and when I ran the codes with my code reader it shows MAP Sensor P000171. Well I have replaced the MAP Sensor, then both the O2 Sensors on the exhaust, the IAC, plugs and wires. Rest the code and after the second time starting it comes on after about 30 miles. Out of ideas.
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2002 Volvo S40 Question: Check Engine Light
Answer #1mastertech6371 April 26, 2011, 20:02Master
171 is not a mass air flow code. a free code pull never identifies a bad part, just a failed system.
it sounds like a vacuum leak or a bad pvc. either way you need help from a shop as you have wasted enough money now on this issue.
try the directory tab at the top of the page for a shop near you.
Answer #2Bret Bodas April 26, 2011, 20:57Master
You can find info on how to diagnose this code here>> http://repairpal.com/OBD-II-Code-P0171-and-P0174
I agree with Roy 100%. Your approach has been a waste of money. Such a shame. Take it to a professional and have it looked at. It's probably a split vacuum hose or leaking intake manifold gasket.