Traction Control

DESCRIPTION
Traction Control is a function of the Powertrain Control Module (PCM) and the Electronic Brake and Traction Control Module (EBTCM) that reduces front wheel slip during acceleration by applying the front brakes and reducing engine power. Refer to Transmission and Drivetrain for an explanation of the EBTCM's role in traction control. The PCM continuously sends out a Pulse Width Modulation (PWM) signal on CKT 464 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 on CKT 463. 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 via CKT 463, the PCM will disable between one and seven fuel injectors to achieve this.

OPERATION
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% 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.

TRACTION CONTROL DISABLE
Several diagnostic codes disable traction control when set. They will also trigger the TRACTION DISABLED message on the Driver Information Center (DIC). PCM Override PS24 also disables traction control and triggers the message. To diagnose a Traction Disabled message, diagnose any codes set first. Then check PCM Override PS24 and, if active, deactivate the override. If the TRACTION DISABLED message is still present, refer to Transmission and Drivetrain for further diagnosis.