t SHT
The ECM transmission control valve has a built-in
redundant shutdown solenoid and a pressure switch
that monitors the pressure controlled by that solenoid.
This solenoid is controlled by the APC200 using
both a high side and a low side switch.
When the controller enters shutdown mode, all four
pressure modulators are put at zero and both controlling
outputs of the redundant shutdown solenoid are
switched off.
This mode is activated when a severe internal or external
problem is detected. If it is an intermittent
problem, the controller will exit the shutdown mode
and enter the Limp Home mode.
However, in case the error is related to the pressure
feedback signal, Shutdown mode remains selected
until the controller is switched off.
When a fault related to the parameter settings located
in the FLASH memory is detected, the controller
reverts to Shutdown mode
Pressure Feedback Sensor
The pressure feedback signal is evaluated as an
ON/OFF pressure switch, with internal resistance of
2 kOhms when open and kOhms when pressurized.
If resistance is substantially lower than 1 kOhm, a
shortcut (SC) condition is assumed.
If it's higher than 2 kOhms, an open load (OL) condition
is assumed.