SAAB WIS ONLINE

Transmission control module (TCM)

Transmission control module (TCM)



DRIVE

When the selector lever on a car with automatic transmission is moved to any position except P or N, current (B+ circuit) is applied to pin 14 of the Trionic electronic control module. The electronic control module then opens the idle air control valve slightly wider to compensate for the increase in load. Pin 14 is not used on cars with a manual gearbox.

If a gear position other than P or N is selected, the ignition timing will also be temporarily retarded, depending on throttle position, in order to protect the automatic transmission.

CHECK ENGINE request

If an emission-related fault arises in the automatic transmission, its control module will send a 2 Hz PWM signal to pin 61 of the Trionic electronic control module. The Trionic electronic control module then causes the CHECK ENGINE lamp (MIL) to light up. When the ignition switch is turned to the ON position, the transmission control module emits a ground pulse for 1 second as a test.


Torque reduction

The transmission control module grounds pin 13 of the Trionic ECM on gear-changing. The Trionic system then retards ignition to make gear-changing smoother and protect the automatic transmission.

During the gear-changing process, ignition will occur between 17° BTDC and 10° ATDC, depending on engine speed and load.


Brakes

When the brake pedal is depressed, current (B+) is applied to pin 15 of the electronic control module. If the brake pedal and accelerator are both depressed and engine speed is below 3000 rpm, the ignition timing will be retarded. The purpose of this is to protect the transmission if the engine stalls.