Allante V8-273 4.5L (1991)
Fluid Pressure Sensor/Switch: Description and Operation
PCM Wiring
DESCRIPTION:
The second gear pressure switch is a normally closed switch located within the transmission. This switch is opened by second gear oil when the
line pressure is high enough to allow shifts without clutch slippage. EI79 displays the voltage status of the second gear pressure switch input (PCM
terminal C10). When the switch is closed the input will be LO and will switch HI when the vehicle is in second, third or fourth gear with sufficient
line pressure to allow 3-2 downshifts.
Transmission line pressure is regulated by the vacuum modulator in response to intake manifold vacuum. At high engine load (low vacuum) the
line pressure is high, and at low load the pressure is low. The PCM calculates engine vacuum by subtracting MAP from BARO. If under the given
vacuum conditions EI79 is not correct, the code will set.
DIAGNOSTIC NOTES:
A failure in the 2nd gear pressure switch may cause a diagnostic trouble code E050 to set.
