2010 Mazda 3 No Communication With PCM, No Start, No Crank

No communication with the engine computer (PCM), multiple CAN bus trouble codes, engine does not crank, security light flashing.
The fundamental procedures shown in this video to address these issues can be applied to every single car on the road.

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Video breakdown
- testing the 5v reference circuit 1:10
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- relay testing fundamentals (main relay) 3:53
- testing the PCM control of the main relay 8:33
- using a test light to energize the control side of a relay 10:00
- dead fuse tests after jumping main relay 11:58
- why the test light should be used and not a jumper wire 12:15
- open circuit between fuse box and PCM identified 15:00
- 5v reference test after repair 15:40
- main relay control wire test at the fuse box connector 17:08

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-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!

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