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

Рет қаралды 20,013

11 жыл бұрын

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
www.jbtoolsales.com/autel-ms9...
- PicoScope 4425 4 Channel Standard Diagnostic Kit
www.aeswave.com/cart.php?m=aff...
Playlist
- (Chapters 9, 10 and 11) The 5v Reference and Signal Circuit Quick Tests
• (Chapters 9, 10 and 11...
Related videos
- How to test a GM MAF Sensor (Part 1)
• How to test a GM MAF S...
- How to test a GM MAF Sensor (Part 2)
• How to test a GM MAF S...
- How to test a MAF sensor using a Picoscope - GM
• How to test a MAF sens...
- Dirty MAF Sensor Case Study
• Dirty MAF Sensor Case ...
- Ford 4-wire MAF sensor wiring tests (integrity testing)
• Ford 4-wire MAF sensor...
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 www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
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.

Пікірлер: 25

@telmosouza 11 жыл бұрын

I have 25 years of experience, I was solving the cars problems based on my practice, and sometimes I was wrong. So I decided to recycle me, I found your channel and i not only recalled, but also i learned a lot. I traded my old oscilloscope by Snapon Verus, and in five minutes I fixed an intermittent problem on my car, that annoyed me for almost 1 year, As a thank you, I will buy your book, and I ask that you continue your work, which has helped to improve my knowledge and others people too.

@sivucit 11 жыл бұрын

very good, I learn one or other thing in every other video, don't know when I will stop learning..

@ScannerDanner 11 жыл бұрын

Thank you! I really appreciate your support.

@victor35ma 11 жыл бұрын

Good demonstration.. When it comes to MAF no matter which year or make it is, time is money and MAF got technicians nuts in the pass, not anymore ... remember auto shop must be productive and MAF must be diagnosed in 10 min or less. So, we use Volumetric Efficiency test or VE test to cut time and dimes. Using SVerus you r able to determine the MAF state by setting up 2 PID: grams per second and RPM. Send me a private message and I will try to give all details. Thanks for your video trainings.

@LynxStarAuto 11 жыл бұрын

@trad444 there are "base values" you can reference provided by the manufacturer for diagnostic purposes. However these values should not be your only method to determining whether a MAF is bad or not. Simply as Paul stated many things can affect the performance of the sensor. A vacuum leak for ex, will affect the idle signal the sensor produces. For this reason you must eliminate every variable.

@fabioapolinario1 11 жыл бұрын

thanks again!!!!!!. and have a great week

@ScannerDanner 11 жыл бұрын

Lots of variables to that question. Every engine "breathes" differently. You need to be familiar with the engine you are working on for sure.. Then also by looking at fuel trim numbers as a guide. Another one I use is O2 at WOT to let me know if fuel delivery is good or not. Keep in mind there are other variables that cause MAF related issues and codes (plugged exhaust, plugged air filter etc)

@jajabor01010101 11 жыл бұрын

Thank you for your big voice.

@ScannerDanner 11 жыл бұрын

Thank you Jerrod. I'll check it out

@TheOvnicar 11 жыл бұрын

very good video my friend Paul keep going

@jerrodwilliams6789 11 жыл бұрын

Check for updates with your shopstream update tool they just rolled out with a huge critical update. It adds the "ask a tech" selection to the main screen. It also updates the scanner modules and gives you more options with the scope!

@estrelladelnorte1308 11 жыл бұрын

very nice ! thank you Sr!

@malisa696 11 жыл бұрын

great video mister Danner. Thanks.. :)

@stage3performance 11 жыл бұрын

Hey Paul, I know you may have been this many times, but I'm going to buy a scope this week and I'm tied between the Snap-in Vantage pro and the Picoscope. I can only afford a 2-channel scope at the moment, but my question is which one would you pick? I just finished reading your book and watching all of your videos so I'm ready to start implementing your techniques. I greatly appreciate any advice. Thanks again!

@dmorley100 11 жыл бұрын

Since this was an old school GM MAF problem, I was wondering if you were gonna show either the connector wiggle test or the screwdriver tap test, lol.

@MrXyzasdf 11 жыл бұрын

Can the calculated load PID be used as a valid VE test?

@Turbotomass 11 жыл бұрын

Doesn't global obd2 not show substituted valves?

@rlwillett 11 жыл бұрын

Paul, I was curious if you've ever used a sun ls2000 2 channel I've acquired one and need to rebuild it but wanted to know if it might be worth it

@LynxStarAuto 11 жыл бұрын

Also to the guys claiming VE testing. While VE testing can point you in the right direction, it is not a fail safe method to single out a bad MAF. What happens if you have a mechanical issue(s) with the engine? There are just too many variables related with a MAF signal, and how it's generated. Better to be safe than sorry. While a quick fix is great for your pocket, so is customer integrity.

@ScannerDanner 11 жыл бұрын

no, they are not allowed to in that mode from what I have been told.

@victor35ma 11 жыл бұрын

yes it can... but in my opinion you have to also do a VE test. to rule out MAF.

@redclift30 11 жыл бұрын

There goes that ground relocation again to remove the noise.

@LynxStarAuto 11 жыл бұрын

The Verus has come a long way. Upon release it was clumsy and cumbersome.

@squack90 10 жыл бұрын

my maf did not throw a code.I have been to a lot of repair shops .new fuel inj new distributor knock sensor.I unplug maf truck ran a lot better .no body could find it

@ScannerDanner 11 жыл бұрын

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