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.

There is plenty of proof that 80% of the top 10 emission diagnostic trouble codes (DTCs) can be solved by diagnosing the data from the global side of a scan tool. 

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.