Traction Control

Traction control is a function of the PCM and the Electronic Brake Traction Control Module (EBTCM) that reduces front wheel slip during acceleration by applying the front brakes and reducing engine power. Refer to Traction Control System found within ABS Operation in Brakes and Traction Control for an explanation of the role of the EBTCM in traction control. The PCM continuously sends out a Pulse Width Modulated (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 the EBTCM senses the front wheels slipping. The EBTCM may 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. The PCM reduces engine torque by adjusting the ignition timing.

Desired Torque will normally be a 90 percent duty cycle signal to the PCM. When the EBTCM decides to request reduced engine power, the EBTCM 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 upon the percent torque reduction requested. The PCM does not shut off any fuel injectors if any of the following conditions are present:
^ The engine coolant temperature is less than -40°C (-40°F) or more than 131°C (268°F).
^ The engine coolant level is low.
^ The engine speed is less than 600 RPM.

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

Several DTCs disable traction control when set. The DTCs 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 test the traction control override and, if active, deactivate the override. If the TRACTION OFF light/message is still present, refer to A Diagnostic System Check - in Antilock Brake System for further diagnosis.