Bill Fulton is the author of Mitchell 1's Advanced Engine Performance Diagnostics and Advanced Engine Diagnostics manuals. He is also the author of several lab scope and drivability manuals such as Ford, Toyota, GM and Chrysler OBD I and OBD II systems, fuel system testing, many other training manuals in addition to his own 101 Lab Scope Testing Tips. He is a certified Master Technician with over 30 years of training and R&D experience. He was rated in the top three nationally on Motor Service magazine's Top Technical Trainer Award and has instructed for Mitchell 1, Precision Tune, OTC, O'Reilly Auto Parts, BWD, JD Byrider, Snap-on Vetronix and Standard Ignition programs. You may have also seen Fulton in many Lightning Bolt Training videos and DVDs and read his articles in many auto service magazines. He currently owns and operates Ohio Automotive Technology, which is an automotive repair and research development center.
All technicians are aware that the scan tool holds the No. 1 priority in our initial diagnostic strategies. In my personal experience, the No. 2 tool in diagnostics is the DVOM, known as the digital volt-ohm meter or multimeter. In the event of an electrical problem, the DVOM is the essential tool.
We as automotive technicians all get the intermittent problems or symptoms from a customer’s car that we know can take a lot of diagnostic time to duplicate the symptom and a lot of diagnostic tests. Even so, there are times in all of our encounters when we are forced to make a judgment call as to what component we may feel is causing the intermittent problem.
If we go back to the early electronic fuel injection, (EFI) systems known as batch-fired injectors or what was called simultaneous EFI systems, the bank 1 injectors were all fired together. The next engine revolution resulted in the powertrain control module (PCM) group firing the injectors from bank 2. When an injector electrically lost its resistance value or had a problem called pintle distortion, it created a rich condition on that specific cylinder and bank.
You likely have noticed that a significant number of vehicles that have come into your shop lately have six-digit odometer readings. What this could mean is that a mechanical integrity issue may be the cause of a misfire code or a misfire symptom.
We are going to cover the diagnostic value of scope-checking the primary side of the ignition system on a voltage trace and by using a low inductive amp probe to monitor coil charge values and analyze ignition events.
You have certainly heard the phrase that “a picture is worth a thousand words of information.” That especially is true on lab scope waveforms from both sides of the ignition system as well as input sensors and output devices.