I completely rebuilt my truck engine, the only thing I didn't do was take the block out. But I replaced all the gaskets and piston rings. Took it apart and reassembled down to a bolt. Then I drove it 45 mi and the CEL turned on. Got home and plugged the OBD2 to read P0101 -- mass air flow. One thing I did not do was replace the air filter because it looked pretty clean.

How can I go about pinpointing what the cause of this code is? I understand what it means is that the engine is not absorbing the expected volume of air but the causes can be different, such as leaky intake manifold gaskets, which I replaced. Could the sensor itself be broken and need replacement?

1 Answer 1


Yes, the sensor is most likely your problem. Try cleaning your MAF sensor. Use only cleaning solution specified for cleaning the MAF. It is a delicate thing, so be careful with it. If that doesn't work, try exchanging your MAF with a known good one. If that works, you need a new one.

  • so basically, if cleaning the sensor does not clear the code, buy a new sensor, correct?
    – amphibient
    Dec 8, 2022 at 23:47
  • I found this useful video: youtube.com/watch?v=gRfaPfTcfOM
    – amphibient
    Dec 9, 2022 at 0:01
  • 1
    @amphibient - Before you buy a new sensor, see if you can find a "donor" from some other vehicle to check. Before you buy anything, always know that what you're purchasing is actually needed. A new MAF may not be the ticket, but it sure looks like it from here. Dec 9, 2022 at 2:08
  • yeah, makes sense, except I don't know any "donor". I just cleaned the MAF sensor with the special spray and also replaced the air filter, which did look kinda bad on a second look
    – amphibient
    Dec 9, 2022 at 3:29
  • Use an OBD reader to read the live values from the MAF. You should be able to get it to draw a live graph. Check if the graph looks something like expected.
    – HandyHowie
    Dec 9, 2022 at 8:57

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