Traction Control System

Traction Control System Components:

TRACTION CONTROL SYSTEM
The Traction Control (TC) system is used only on vehicles containing automatic transaxle and ABS. The traction control system is composed of the traction enable switch with LED, traction active lamp, ABS wheel speed sensors, ABS controller, and the PCM's control of spark timing, fuel injectors and transaxle upshift. The PCM monitors the wheel slip and the status of the traction switch. The data is received from the ABS controller. When traction is in the enable mode (switch on) and the PCM see's wheel slip of 0.5 mph during cruising or 2 mph during launch, the PCM begins to retard the spark timing to limit torque to the wheels. If wheel slip continues the PCM will command a transaxle upshift one gear at a time until fourth gear is reached. If slip is still present, the PCM will reduce the authority of the spark system, and control slip by toggling the fuel injectors on and off.

TRACTION CONTROL SWITCH
The traction control switch is a momentary contact switch read by the ABS controller, with the ABS also controlling the status of the LED. When the light is On, traction system is enabled and with the light Off, the traction system is disabled. At engine start, (no malfunctions present) traction control system is enabled regardless of previous switch state and the ABS controller illuminates the TC LED. The ABS controller continues to monitor TC switch for a change in state. If traction control is disabled for any reason other than driver input (turning switch Off), the LED will be turned off and the malfunction indicator lamp or Anti-lock telltale will be turned on to indicate malfunction. At this time the ABS controller will store switch status as being On although system and LED are Off. This is to prevent repeated toggling of the TC switch leaving switch status in Off when traction control becomes available again. If the malfunction goes away, the TC LED will light and the TC system will be enabled.

PCM INTERACTION WITH TRACTION CONTROL
The PCM is the "master" of the traction control system receiving inputs on TC switch and wheel speed status from the ABS controller. The PCM looks at this data then verifies no EC/TC (Engine or Transaxle) codes are present and commands the ABS controller to turn on the traction LED, indicating traction control system is enabled. The PCM will disable the traction control system under the following conditions:
^ The driver presses the TC switch, requesting Off.
^ The ABS controller has indicated wheel speed sensor problems to the PCM. (One of diagnostic trouble codes 21-28 is set).
^ No serial data communication between the PCM and ABS controller.

If PCM/EC (EC = Engine Control) diagnostic codes 41 or 42 are set, the PCM will use fuel mode control only.
If PCM/EC diagnostic codes 33 or 34 are set, the system will operate but system response time will be delayed.
The maximum spark authority of the PCM is -20 for the DOHC and -12 for the SOHC.

ABS CONTROLLER INTERACTION WITH TRACTION CONTROL
The ABS controller takes the average of the two front wheel speeds minus the average of the two rear speed sensor inputs and calculates wheel slip. It then determines the status of the TC switch and communicates this data to the PCM initiating spark control. The ABS controller also turns the TC LED On or Off depending on the command from the PCM.

TRACTION ACTIVE TELLTALE
The traction active telltale is located in the instrument panel cluster. When the traction control system attempts to prevent wheel slip, the traction active telltale will begin to flash. This indicates traction system is currently working.

TRACTION CONTROL USE WITH CHAINS OR SPARE TIRE
The traction control system can be used with chains or the spare tire. The traction control system can be turned Off for improved vehicle launch while using chains.

OPTION BIT STATUS
Traction control vehicles must be programmed with auto transaxle options in both the PCM and the ABS controller for proper system operation. If the ABS controller is programmed for a manual transaxle but has TC, no codes will set and the TC LED cannot be turned Off.