Shift Solenoids

Shift Solenoids Description

To provide the different driving characterisUcs for each mode of operation, the TCM incorporates different shift maps of throttle position/road speed. Base shift points are derived from the appropriate shift map. When a shift is required, the TCM sends a request to the ECM for a reduction in engine torque, in order to produce a smoother shift. The percentage of torque reduction requested varies according to the operating conditions at the time of the request. When the TCM receives confirmation of the torque reduction from the ECM, it then signals the shift solenoid valves in the gearbox to produce the shift. To further improve shift quality, the TCM also signals the pressure regulating solenoid valve to modulate the hydraulic pressure and so control the rate of engagement and disengagement of the brake clutches.

There are two diagnostic checks for each shift solenoid, an error is detected if:
1. The ignition supply is greater than 9V and the solenoid voltage is greater than 2.5V with the driver OFF.
This indicates a short circuit to baffery positive.
2. The ignition supply is greater than 9V and the solenoid voltage is less than 3.5V with the driver ON.
This indicates an open circuit or a short circuit to ground.

For the diagnostic table, please refer to the individual codes (i.e. P0753 or P0758).

If the above table does not include details of the following enabling conditions: - IAT, ECT, vehicle speed range, and time after engine start-up then the state of these parameters has no influence upon the execution of the monitor.