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





The function of the three solenoid valves is to control the flow of transmission oil to the various transmission components. Three solenoid valves are located within the transmission assembly, and are closed when not energized.

Pressure Regulator





The function of the five pressure regulators is to modulate the oil pressure to the various transmission components. The regulators are pulse width modulated by the TCM, switching to ground potential. The other side of the regulators being connected, via an internal TCM relay, to battery voltage. The regulator is closed when not energized by the TCM.