The tests shown in this video are not manufacturer specific and will apply to all cars. Circuit identification is the first step in accurate troubleshooting of any output solenoid. Every single step in troubleshooting a computer output, whether it be a solenoid, light bulb, motor or relay, revolves around knowing the design of the circuit. If you do not know the circuit design, then you will be forced to follow some poorly written manufacturer flowchart, which mostly results in improper diagnosis.

Engine Performance Diagnostics chapter 3 pages 3-6

test shown enh 50

  • how to identify solenoid circuit design with a voltmeter
  • how to determine, without a wiring diagram, which wire is the control wire

Tools used

  • digital multimeter
  • back-probing tools

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(Chapter 3) Transistors, Solenoids, Computer Controlled Output Testing

Related videos:

How to test a computer controlled solenoid (energizing the circuit manually) :


How to test a computer transistor driver (without a scan tool):


How to test a computer transistor driver (using a scan tool):


How to test a computer controlled solenoid (power/ground side identification) :


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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available 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. 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!