When an automatic transmission is malfunctioning, it may exhibit one or more symptoms, such as harsh or delayed shifting, the loss of one or more gears, engine RPM "flare ups" between shifts, fluid leaks, slipping or lack of power to the drive wheels, and/or Check Engine Light or transmission overdrive illumination. When these types of symptoms occur, it is important to have an Automatic Transmission Diagnosis.
An Automatic Transmission Diagnosis involves special computer system scan tools, specialized hydraulic pressure testing equipment, advanced technician training, and even licensing in some states. Merely retrieving a code and trying a part, without an Automatic Transmission Diagnosis, will do little to repair the problem and may even damage expensive automatic transmission or emission control components.
The purpose of this article is to provide an outline for some of the essential steps involved in performing an Automatic Transmission Diagnosis. This guide can be used—by you and the shop—to track the progress as the mechanics perform the Automatic Transmission Diagnosis.