Giammalvo Files
Mark Giammalvo

Mark Giammalvo specializes in driveability diagnostics at his family business, Sam Giammalvo's Auto Sales & Service, Inc. in New Bedford, MA.   

Mark, who has been with the business for over 20 years, is an ASE  Master Technician and Parts Specialist. He also holds the ASE L1 certification, and has an associates degree in business management.
Mark is also a writer for Motor Age Magazine and is the past secretary of the Alliance of Automotive Service Professionals, (AASP).

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(Printed in the Journal of The Alliance of Automotive Service Providers, AASP) 

Can't you just hook it up to that computer that tells you what's wrong?

I am amazed that I still get phone calls from people asking if we have "One of those big console computers that fixes cars." Or my favorite, "Can't you just hook it up to that computer that tells you what's wrong?" "Yes, absolutely," I tell them. As a mater of fact, we turn that big behemoth on every morning. Not that we use it anymore, but the public sure wants to see that we still have that magical, huge 5' X 5' box with all its buttons and the big screen. It does look pretty, all lit up with its fancy display. Heck, our model even talks to you. It looks like a computer from Star Trek, the original series that is.

Ah, how I can remember back in the early 80's how amazed I was when the sales agents from Sun Electronics brought it in. It was the Sun Interrogator, and I remember the cost too, about $27,000. In those days cars were just starting to use onboard computers with datastream information that we could access. They called the data "telemetry" back then. How amazing it was to hook up the Interrogator to a vehicle and view the car's computer data as it was transmitted with the engine idling. Wow, Engine speed, Oxygen Sensor Signal, and Air Flow readings. Back then we could even attach a large cassette tape recorder and record the telemetry data during a test drive. Then we would return to the shop and play it back on the Interrogator.  Although to the human ear it sounded like fax tones, the Interrogator displayed it as actual recorded sensor data.

Nevertheless, the days of using the big computer are gone. Now we have the "Portable Scan Tool" that we can take on the road with us. However, neither of these tools alone ever told anyone what was wrong, nor fixed any car. Big or small, old or new, I have yet to see a computer that "tells you" what is wrong. I am not exactly sure how that misconception ever happened upon the automotive service industry. Our specialized electronic equipment can only show us live data. It is up to the technician to decide what sensor reading is correct and what reading is not. Even today I will hook up a scan tool in the presence of a customer and will be asked: "So what did it say was wrong?"

Sure, the Scan Tool is a big help in our diagnostic routine. But even if the tool finds a fault, it is rarely the end solution. Case in point: Often on GM cars with the supercharged V6 engines, the Scan Tool will find a fault code that says an Oxygen Sensor is stuck reporting lean. That doesn't mean I should rush to replace the Oxygen Sensor. Often on these vehicles the sensor is stuck reporting lean due to an air leak at the supercharger base gasket. That extra air entering the combustion chamber forces the Oxygen Sensor to report a lean reading. The computer sees this lean Oxygen Sensor reading, and bingo, a trouble code is stored for the sensor. It's up to the trained, experienced technician to investigate other possible trouble areas that can fool the computer like this. As a mater of fact I have seen cars with this problem in which the customer has recently paid someone to replace the Oxygen Sensors. Evidently some technician somewhere took the Scan Tool code as gospel.

I guess we have come full circle now. This past Sunday I was at a local antique store. I could not believe my eyes. In the store for sale was one of those old, big, magical computers that tell you what's wrong. And what a value now, the vendor is asking only $35.00. 




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