Substituted values (Scan Data Can Lie To You!) MAF sensor fault

توضیحات:

In this video I cover how to test a 3-wire GM MAF sensor and also show how a scan tool can lie to you. There are many names for this condition (limp home mode, fail safe mode etc) where the scan tool will show default or what I call substituted values. If one isn't careful with this condition, misdiagnosis of good components can occur.

Engine Performance Diagnostics chapter 11

Symptoms
- check engine light (Code 34)
- rough idle

Fix
- replace the MAF sensor

Tests shown
- checking scan data for related PIDs
- how to use a scope to check a digital MAF sensor
- how to view the scope and scanner simultaneously on the Snap-On Verus
- how to check a MAF sensor power and ground, identifying scope noise

Tools used
- Autel MS908 MaxiSYS Automotive Diagnostic & Analysis System - USA Version
https://www.jbtoolsales.com/autel-ms908-maxisys-automotive-diagnostic-analysis-system-usa-version#oid=1014_1
- PicoScope 4425 4 Channel Standard Diagnostic Kit
http://www.aeswave.com/cart.php?m=affiliate_go&affiliateID=60df1b5cf6e5582af6ff81c728f42d0d&go=http://www.aeswave.com/PicoScope-4425-4-Channel-Standard-Diagnostic-Kit-p9276.html

Playlist
- (Chapters 9, 10 and 11) The 5v Reference and Signal Circuit Quick Tests
https://www.youtube.com/playlist?list=PLAFYVCyenqcpP9ykkWb2D16nVEjyQ1eTZ

Related videos
- How to test a GM MAF Sensor (Part 1)
https://youtu.be/p2QLxxstRn8
- How to test a GM MAF Sensor (Part 2)
https://youtu.be/E8sBg7kMbOw
- How to test a MAF sensor using a Picoscope - GM
https://youtu.be/h5KAHv47viw
- Dirty MAF Sensor Case Study
https://youtu.be/Hmt_LNJ9GkI
- Ford 4-wire MAF sensor wiring tests (integrity testing)
https://youtu.be/ejh_ZCntFkE

For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium https://www.scannerdanner.com/join-scannerdanner-premium.html There is a 14 day free trial.
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Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

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