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Diagnostic Troubleshooting on Computer Controlled Engines and Automatic Transmissions

It's important to discuss both engine and transmission problems and diagnostic troubleshooting because they are often interrelated, in that problems within these two areas are so often mistaken for each other. This holds true for both electrical and mechanical problems. We are going to give you a little history so you can better understand why engines and automatic transmission problems can be so difficult to diagnose.

Engine Emissions Controls are Introduced

Up until around 1975, when engine emissions controls began to be introduced, engine problems were relatively easy to perform a diagnosis. From that point through the early 80s, a tangled cluster of vacuum hoses and wires were tossed under the hood, sitting atop the new carburetors and transistorized ignition systems that they supported. These new systems often yielded very poor performance and required many trips to the dealer or auto repair facility. Ironically, many poorly running engines would actually provide the worst gas mileage for cars and trucks than engines built in the 60s. There were many different models, many different problems, and design changes that came year after year. This was the point in time at which the process of diagnosing engine tuning and performance problems became a nightmare. What seemed like a simple tune-up issue may have taken days to diagnose. We believe this was the point at which they coined the phrase, “factory authorized complaint”. This translated to: “We understand what you’re complaining about. We understand why you think it’s a problem. We realize that your engine doesn’t seem to run the way other cars’ engines do or have in the past, but it’s okay just the way it is. The engine starts. The car moves. It won’t blow up.” Obviously, this can be very frustrating.

Engines Become Computer Controlled

A few blew up, but most engines didn’t. Through the 80s, car and truck manufacturers began to replace carburetors with computer-controlled electronic fuel injection systems. Also during this period, electronic (transistorized) ignition distributors using a vacuum and centrifugal advance were replaced with computer-controlled (microprocessor chip) ignition systems. By the late 80s, computer-controlled cars and truck engines had more power, ran smoother, and were much more reliable. Engine problems due to vacuum lines and related valves were slowly overtaken by problems due to wires and electronic sensors. Car and Truck Engine performance issues were still difficult to diagnose, but there were fewer of them.

Transmissions Become Computer Controlled

Throughout this period automatic transmissions were changing as well and soon almost all vehicles had adopted both overdrive and a lockup torque converter. While many of these automatic transmissions did require a few wires, it wasn’t until the late 80s that computer-controlled transmissions began to be employed. Computer control transmissions use microprocessors just as engines do, and in many cases, they share the engines’ microprocessors as well as electronic sensors on cars and trucks. Today, engine and automatic transmission computer control systems are heavily integrated. Unlike the engines, however, the automatic transmissions have become almost fully reliant on the proper operation of the computer-controlled engine and its related electronic components. Suburban has years of experience in diagnosing computer problems and differentiating them from mechanical failures.


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