Kickdown function: Diagnostics
If the function is faulty a diagnostic trouble code is generated in the engine system.
If bus communication with the engine control system has ceased a P1921 diagnostic trouble code is generated, the transmission goes into the limp-home mode.
Inaccurate information on the bus causes diagnostic trouble code P1971 to be generated. Depending on the fault, the TCM may activate the emergency operation program (Limp-Home mode).