Clearing trouble codes (P0101)
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    1. #1
      Member d3box1's Avatar
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      Clearing trouble codes (P0101)

      Howdy there, I just have a quick question. I went to auto zone today, no check engine light or anything however I make a force of habit to have them run a scan tool.

      They run a check- code P0101 MAF failure- I have in the last month replaced the MAF and again, no CEL so I didnt think anything of it but the code was still coming up.

      The guy at auto zone (not even asking first) cleared the code and said all set- No biggie, so I start my car and leave- i feel a woosh of power..... my car has been sluggish as of late so I was surprised.

      My question, clearing a DTC effect your cars performance?

      Example- improper readings from MAF puts the car in limp mode- clear the code back to full power? Maybe like a "safe mode" on cpu's?

    2. #2
      Member Crito's Avatar
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      Quote Originally Posted by d3box1 View Post
      My question, clearing a DTC effect your cars performance?

      Example- improper readings from MAF puts the car in limp mode- clear the code back to full power? Maybe like a "safe mode" on cpu's?
      Affect, and yes. If the engine management system can't get a good reading from a needed sensor it'll use a default (lean) air/fuel ratio mapping. There's a P-code to Volvo-specific code PDF floating around somewhere you might want to check before buying any parts though. If you have VADIS it's in there too. Just saying because I *thought* a MAF code would trigger CEL.... sometimes the MAF is bad and you don't get a code.... but I could be wrong.

    3. #3
      Moderator tmtalpey's Avatar
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      MAF codes usually will trigger a CEL, but they can take a while to do so. The ECU watches for several consecutive drive cycles with the error before it lights up.

      Yes, an ECU reset will clear out behaviors like this, temporarily. Trust me, it's a fleeting solution. If you've replaced the MAF already, look for other issues. Check the intake piping, especially look for air leaks. Also make sure your sensors' connectors are clean and well-seated. Don't forget the IAT/MAP sensor down on the intercooler, assuming you have a T5 (you didn't say). A bad pressure reading can cause the ECU to question its airflow calculations and blame the MAF.
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva CBV, Elevate rear swaybar, Snabb shift kit, etc.
      2004 XC90 2.5T AWD
      1956 PV444 complete, running
      1956 PV444 very original, very rough

    4. #4
      Member d3box1's Avatar
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      thank-you for the comments! Sorry I have a T5 so I can check out the intercooler sensors- how would I go about testing if the sensor is burnt out or needs to be replaced? In the mean while I will check vacuums and take a look to see if I can spot a hole or leak or tear- anything like that.

      Also I will see if the code comes back? I drive quite abit so I am always starting/driving/turning off the car- Im not sure how this works and what counts as a driving cycle- my old S60 you didnt know if the cel was going to re-appear until you drove 400 miles

    5. #5
      Moderator tmtalpey's Avatar
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      The sensor is very unlikely be have failed completely, and it's not easy to test - you'd need a pressure chamber and full specs. Look for air leaks first, especially around the tube thae goes over and behind the engine, the fittings that come off it, and that kind of stuff. Basically, anything *after* the MAF in the plumbing.

      No way to predict when/if the code will come back. Depends on many things, including whether it's a constant or intermittent issue.

      In any case, the "P" codes (P0101 in your case) are generic OBD codes and are nowhere near as accurate for diagnosing issues as the Volvo DTCs. If you have an issue like this that can't be fixed through inspection and simple diagnosis/repair, I recommend a dealer. They can scan MUCH more than this level.
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva CBV, Elevate rear swaybar, Snabb shift kit, etc.
      2004 XC90 2.5T AWD
      1956 PV444 complete, running
      1956 PV444 very original, very rough