The methods shown for testing computer power, ground and 5V reference circuits can be applied to any year/make/model out there. This is a great video on what to do when you’re faced with a no start, no communication problem. The vehicle featured also had no spark, no injection pulse or fuel pressure during testing, all of which pointed me towards an engine computer issue.

Engine Performance Diagnostics chapter 9

Symptoms
- crank no start
- no communication with ECM

Fix
- replaced shorted MAP sensor

Tests shown
- how to check for scan tool communication issues
- using the check engine light during diagnostics
- how to check the 5V reference circuit
- how to check an engine ground for a poor connection
- how to use a wiring diagram to identify computer power and ground circuits
- how to locate the correct pins on a bulk connector using wire sequencing
- verifying your scope ground for testing
- how to check computer power and ground circuits using voltage drop
- how to make sure you’re connected during ground-to-ground voltage drop checks
- understanding 5V reference circuit design
- how to check for shorted 5V reference sensors

Tools used
- Autel MS905 MaxiSys Mini Diagnostic System with Connector Kit - USA Version
[ Ссылка ]
- PicoScope 4425 4 Channel Standard Diagnostic Kit
[ Ссылка ]
- Digital Multimeter [ Ссылка ]

Playlist
- (Chapters 9, 10 and 11) The 5v Reference and Signal Circuit Quick Tests
[ Ссылка ]

Related videos
- Poor running, flashing CEL, no codes (bad computer ground) - Toyota
[ Ссылка ]
- 1996 Jeep No Start Case Study Part I
[ Ссылка ]
- Bad Engine Computer Testing Part 1
[ Ссылка ]
- How to check the 5v reference circuit for a short to ground (Cadillac)
[ Ссылка ]

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 [ Ссылка ] 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.

свернуть