Traction Control

Traction control is a function of the PCM and the Electronic Brake Traction Control Module (EBTCM) that reduces any front wheel slip during acceleration by applying the front brakes and reducing the engine power. Refer to ABS Description or to ABS Description in Antilock Brake System. 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 it sees the front wheels slipping. The EBTCM may decide to apply the front brakes only or to apply the front brakes and request a reduced torque output from the powertrain. The EBTCM requests a 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 a reduced torque output from the powertrain. The PCM reduces the engine torque by adjusting the ignition timing.

The Desired Torque will normally be a 90 percent duty cycle signal to the PCM. When the EBTCM decides to request a reduced engine power, the duty cycle of the Desired Torque signal is decreased by the amount of torque reduction required. A 90 percent duty cycle means no torque reduction, while a 10 percent duty cycle means 100 percenttorque reduction. The PCM responds by shutting off the 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
^ The 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 the traction control ends.

Several DTCs disable the traction control when set. They will also trigger a Traction Off light or message. The PCM traction control override also disables the traction control and triggers the message. To diagnose a Traction Off light or message, diagnose any DTCs set first, then check the traction control override and, if active, deactivate the override. If the Traction Off light or message is still present, refer to A Diagnostic Starting Point or to A Diagnostic Starting Point in Antilock Brake System.