atefitty Posted August 6, 2012 Report Share Posted August 6, 2012 Okay, got a 1998 V70 with a code p0172b. Does this mean it is actually running lean due to a vacuum leak and the ECM is compensating causing it to be rich? The rear o2 is at zero volts. I've swapped out the 02 sensor and cleaned the MAF and checked the vacuum elbow near the thermostat. It's also going into open loop, I'm assuming because it's too lean its staying in open loop. Any ideas on how to fix this? Link to comment Share on other sites More sharing options...
CBoosT5 Posted August 7, 2012 Report Share Posted August 7, 2012 This is usually caused by either 02 or MAF sensor. So yes, I would say you are running lean, and the computer is telling it dump fuel. I would check for any major vacuum leaks seeing as you covered the basics.Does the car have a long crank? I would also look into fuel pressure regulator. Did you check front o2 while you checked the rear?Ah, a bad PCV will also call this, keep thinking of more everytime I go to a different thread haha. Link to comment Share on other sites More sharing options...
atefitty Posted August 7, 2012 Author Report Share Posted August 7, 2012 I cleaned the Maf as I said and swapped out the rear o2...Front o2 readings seem normal. car starts up great and runs fine..I plan to check fuel pressure next.. Hadn't thought about PCV and skeptical of that being the cause. there is some blowby at the dipstick but not excessive..I will check the Flametrap to see if it is blocked. Thanks for your reply Link to comment Share on other sites More sharing options...
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