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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?

Pᴀᴜʟsᴛᴇʀ2
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amphibient
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1 Answers1

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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.

Pᴀᴜʟsᴛᴇʀ2
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  • so basically, if cleaning the sensor does not clear the code, buy a new sensor, correct? – amphibient Dec 08 '22 at 23:47
  • I found this useful video: https://www.youtube.com/watch?v=gRfaPfTcfOM – amphibient Dec 09 '22 at 00:01
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    @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. – Pᴀᴜʟsᴛᴇʀ2 Dec 09 '22 at 02:08
  • 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 09 '22 at 03:29
  • 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 09 '22 at 08:57
  • Before buying anything check the wiring carefully. Note that in some vehicles there may be more than one connector that fits. So you may have the MAF wire switched with some other wire. – jwh20 Dec 09 '22 at 15:39
  • this seems to have fixed the problem – amphibient Dec 10 '22 at 18:19
  • @HandyHowie -- i have a "stupid" OBD2 that only reads codes. any recommendation for a more sophisticated one that reads engine params ? – amphibient Dec 10 '22 at 18:19
  • @amphibient - If you can get an ELM327 based Bluetooth one, then get apps for your phone (like Torque Lite), it'll do the live data for you very cheaply. You can get a Chinesium type ELM327 off of Amazon for under $20. – Pᴀᴜʟsᴛᴇʀ2 Dec 10 '22 at 18:34
  • is that similar to BlueDriver? I used my buddy's bluedriver and it didn't give me those detailed statistics – amphibient Dec 10 '22 at 20:20
  • https://www.amazon.com/obdator-Bluetooth-Scanner-Automotive-Diagnostic/dp/B074DWH8JR/+ – Pᴀᴜʟsᴛᴇʀ2 Dec 10 '22 at 20:31
  • @Pᴀᴜʟsᴛᴇʀ2 -- after I cleaned the old sensor and replaced the air filter, the CEL went away but only for 150 mi and then it came back. So because the sensor is only about $26 with shipping, I ordered a new one. But here is a question: when I install it, should I reset the CEL (erase the code) and wait for it to perform the engine sensor testing from 0 or should I leave it as is and see if the CEL will go away? – amphibient Jan 14 '23 at 15:20
  • @Pᴀᴜʟsᴛᴇʀ2, you can actually post that answer here – amphibient Jan 14 '23 at 15:30