XK-8 Coupe (X100) V8-4.0L (AJ26) (1998)
Valve Body: Description and Operation
Hydraulic Control - Transmission Pressure Regulators and Shift Solenoids
Operation
Fluid flow within the transmission assembly is controlled by three solenoid valves and five pressure regulators.
The Transmission Control Module (TCM) supplies an internally switched +12 Volt supply to each shift solenoid and pressure regulator. Hydraulic
pressure from the pressure regulators is controlled by 'Pulse Width Modulation' (PWM) of the ground switching signal i.e. the duty cycle; the time
that the pressure regulator is switched on. Control of the solenoids is effected by switching one side to ground through the TCM.
During normal operation the TCM monitors 'Switch On' of the solenoids, the regulators and the TCM output stages, but does not check the output
stage 'Switch Off'.
Voltage is monitored at the regulators and solenoids for continuity and shorts. For example, when a solenoid is ON the voltage on the TCM side
should be ground, when OFF the voltage should be +12.
Shift Solenoid