In this video I’ll show you how to retrieve trouble codes from an OBD-I vehicle, a 1991 Eagle Talon (which is a Mitsubishi Eclipse), and how to test a throttle position sensor with a graphing multimeter. The TPS testing shown will also work on all three-wire potentiometers, and can be applied to any vehicle. The code retrieval procedure shown is make/model specific, so consult your service information for your application.

Engine Performance Diagnostics chapter 7

symptoms 50

  • intermittent check engine light illumination
  • hesitation on acceleration
  • surging idle

fix 50

  • replace faulty throttle position sensor

test shown enh 50

  • retrieving trouble codes manually from an OBD-I vehicle
  • using a graphing multimeter during trouble code retrieval
  • how to test a 3-wire potentiometer without a wiring diagram (all types)
  • performing a TPS ‘sweep test’ using a graphing multimeter
  • using heat and vibration to expose electrical faults

Tools used

  • graphing multimeter

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(Chapter 7) Potentiometer-position sensor tests TPS, EVP, APP, VAF etc

Related videos:

How to test TPS wiring with a scan tool (any car):


How to test throttle position sensor wiring with a resistor (any car):


Throttle Position Sensor test (voltmeter and scope):


How to test a throttle position sensor (P0121, P0122) GM wiring integrity:


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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!