Transmission malfunctions can be caused by a variety reasons, both inside the transmission and out, according to Wayne Colonna, who presented “Transmission and Drivability Diagnostics” Saturday morning at Automechanika Chicago.
His course provided diagnostic tips to help determine if the problem is with the transmission or elsewhere. For example, a transmission problem could be caused by a malfunction related to an engine management problem, an anti-lock braking system (ABS) issue or an actual transmission malfunction, he said. Finding the root cause can be challenging and time consuming.
The list begins with information, which means first looking to see if there are any bulletins or articles already covering the subject. The available diagnostic equipment as well as the ability to use the equipment is considered if handling the problem over the phone.
Understanding the codes received, checking power and grounds, doing a cursory view of the wiring and connectors while looking for cross connect possibilities are on this list. Checking into the four main critical PCM/TCM inputs (engine load, speed sensors, gear shift position switches or sensor and temperatures) as well as how the signal is generated and delivered to the controlling computer and computer strategies (ABS, torque reduction, failsafe, sport and economy modes, adaptations, manual tap shift controls, start/stop technology or neutral controls, etc.), transmission mis-application, transmission fluid and aftermarket programming, products and parts round out the list.
Having this comprehensive overview goes a long way in determining which avenue one needs to take based on the problem at hand to get to the cause as quickly as possible, he said. While this doesn't completely eliminate every possible problem, it can eliminate many of them.
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