The Trainer #141: Capitalizing on multiple scan tool functions for transmission analysis

Sept. 29, 2023
Using a capable scan tool's features to diagnose transmission concerns is a recipe for efficient transmission diagnostics.

In my experience navigating through dozens of shops over the last two decades, it’s quite common to find that one of the largest areas of mystery lies with the automatic transmission. Its intricacies include electrical and electronic control of hydraulic circuits to create mechanical outputs. All of them require an inquisitive mindset and gentle touch, and care must be taken during disassembly, inspection, reassembly, and verification processes. But all of that applies only after committing to disassembly.

Like all facets of the automobile, technology continues to find its way into every component we encounter, including the automatic transmission. Electronic components like transistors and MOSFETs within the transmission control modules or PCMs drive or control solenoids, and it’s these solenoids that will route pressurized hydraulic fluid accordingly to create mechanical movement of the components within the transmission, allow the vehicle to drive down our motorways.     However, we are faced with that initial question at the point a failure occurs. “Is the problem inside or outside the transmission?” And it’s that very question they may mean the difference between a successful/affordable repair or the customer getting rid of the vehicle because the cost of transmission replacement exceeds the value of the car. It’s important we determine easily that the electrical components have everything they need to function and are indeed functioning correctly before condemning a transmission for disassembly.

In this episode using a diagnostic platform and its multiple features will aid in an efficient diagnosis of a transmission related driveability concern. Beginning in the driver's seat, a global scan for DTCs will be carried out followed by a comprehensive road test capturing graphed transmission data PIDs for analysis. This will lead to logical testing of the solenoids and related circuitry responsible for delivering the pressurized hydraulic transmission fluid to the respective hydraulic components internal to the transaxle. Stick with Motor Age magazine’s Technical Editor Brandon Steckler as he walks you through a logical approach to automatic transmission analysis and diagnosis. 

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