Traction Control - Cadillac 1999 Seville SLS V8-4.6L VIN Y Service Manual

Traction Control is a function of the PCM and the EBTCM that reduces front wheel slip during acceleration by applying the front brakes and reducing engine power. Refer to Brakes for an explanation of the EBTCMs role in traction control. The PCM continuously sends out a PWM signal that indicates the torque output of the powertrain. This signal, referred to as the Delivered Torque signal, is used by the EBTCM to determine what action is required when it sees the front wheels slipping. The EBTCM may decide to apply the front brakes only or apply the front brakes and request reduced torque output from the powertrain. The EBTCM requests reduced torque using another PWM signal. This signal, referred to as the Desired Torque signal, is used by the PCM to determine if the EBTCM is requesting reduced torque output from the powertrain. If the EBTCM requests reduced torque, the PCM will disable between one and seven fuel injectors to achieve this.

Desired Torque will normally be a 90 percent duty cycle signal to the PCM. When the EBTCM decides to request reduced engine power, it decreases the duty cycle of the Desired Torque signal by the amount of torque reduction required (90 percent duty cycle means no torque reduction, 10 percent duty cycle means 100 percent torque reduction). The PCM responds by shutting off fuel to one or more cylinders depending on the percent torque reduction requested. The PCM will not shut off any fuel injectors if any of the following conditions are present
^ Coolant temperature is below -40°C (-40°F) or above 131°C (268°F).
^ A low coolant level is present.
^ Engine speed is below 600 rpm

The disabled fuel injectors will be re-enabled one by one as the need for traction control ends.

Several DTCs disable traction control when set. They will also trigger a TRACTION OFF light or message. The PCM traction control override also disables traction control and triggers the message. To diagnose a Traction Off light/message, diagnose any DTCs set first. Then check the traction control override and, if active, deactivate the override. If the TRACTION OFF light/message is still present, refer to Brakes for further diagnosis.