Permanent Program Functions

Permanent functions

Apart from the driving modes which can be selected manually by the driver (E, S and W), the system incorporates a number of permanently preprogrammed TCM functions to ensure that the correct gear is selected at all times in relation to external conditions which, in most cases, produce a change in load or temperature in or around the engine and transmission. The permanent special functions are:

A When driving at altitude, gearshifting is adapted to match the reduced engine load by adjusting the gear engagement times to prevailing conditions.
B If the TCM detects that the throttle is closed although the speed of the car is increasing, for example when using engine braking on a steep downhill gradient, downshifting to 3rd is performed automatically to maintain engine braking and reduce wear on the ordinary brakes.
C If the transmission temperature rises abnormally due to increased loading at high ambient temperature, the lock-up function is activated as often as possible to reduce slip and the generation of heat in the unit.The line pressure is increased at low ambient temperatures, enabling gear engagement times to be shortened.
D The system incorporates safety functions to prevent manual engagement of 2nd or 1st gear if the speed of the car is too high.
E Reverse gear cannot be engaged at speeds over 5 km/h.
F In the event of a serious fault in the electronic control system, the MIL on the combined instrument and the driving mode selector lamp will flash, while the TCM will adopt one of two special programs, an emergency program and a 'limp-home' program.

The emergency program permits automatic gearshifting without torque reduction or other refinements, the degree of simplification depending on the nature of the fault.

The limp-home program switches out the TCM so that the car can be driven by manual gearshifting only. Positions 3 and L provide 3rd gear, while position D gives 4th and R reverse gear.

While the particular program adopted depends on the nature of the fault, the car must be driven to the nearest workshop in either case. The limp-home program is cancelled if the fault does not reappear when the ignition is next switched on. In addition, the MIL will stop flashing when the ignition is switched off and on a number of times, the number depending on which fault has initiated the program.

However, since the DTC is stored in a special memory, it can be displayed later.