When any problem is detected, the computer will memorize a diagnostic fault code. A mechanic will connect a scanner that can access that computer to read the codes. Those codes will lead him to the circuit or system with the problem, not necessarily the defective part.
The scanner will also read the "clutch volume index, (CVI). That is a set of four numbers corresponding to the volume of fluid, in ccs, that it takes to apply each clutch pack. Experienced transmission specialists can tell how much clutch plate wear has taken place based on those numbers.
When the system is shut down by the computer, the solenoid pack is spring-loaded to allow operation in second gear. That's called "limp-in" mode and it allows you to drive slowly to a repair shop without needing a tow truck.
Thursday, November 18th, 2010 AT 4:43 AM