Traction Control (TCS) & Electronic Stability
TCS (Traction Control System) is an anti-slip function which provides improved traction for your vehicle. The control module will reduce engine torque and control braking power to each wheel if the TCS is activated. When one of the front wheels rotates faster than the rear wheels, the TCS senses wheel spin. The magnitude of this wheel spin and the speed of the car are decisive to how the system operates. Traction is given priority when wheel spin exceeds a limit value when the speed is lower than 35 MPH. The system then employs brake application first and then engine torque limitation. The transfer of lateral forces to maintain steering ability is given priority when wheel spin exceeds a limit value at speeds above 35 MPH. The system employs engine torque limitation first & then moves to the deduction of wheel spin. A degree of wheel spin is always allowed so that the sporty feel and handling of the car remains. How aggressively the car is being driven will determine how much influence the traction control devices employ.
ESP (Electronic Stability Program) is a system that assists the driver in stabilizing the vehicle in unexpected situations that would otherwise be difficult to handle by regulating engine torque and brake application. The ESP, ABS, and TCS functions work both independently and in combination with the same control module. Certain functions may continue to operate despite a lit “ESP off” warning lamp. When ESP engages due to a skid, for example, it can counter the skid by applying the brakes on one or more wheels without the driver having to touch the brake pedal. The engine power is also limited by the ESP control module requesting a certain engine torque to reduce the risk of spin on the front wheels. The engine control module regulates the engine torque based on this request. ESP regulates instantaneously at high frequency according to the prevailing conditions. The system receives information from a number of sensors and measures: wheel speed, lateral acceleration, yaw rate, steering wheel angle, and brake pressure. These values are used by the ESP control module that is integrated in the hydraulic unit. The control module calculates the course of the vehicle continuously and compares the value (the direction in which the vehicle is traveling) with the desired value (the direction the driver has chosen with the steering wheel). If the actual value does not agree with the desired value, the system will engage as necessary to apply the brakes on one or more wheels and limit engine torque. If the car starts to under steer (when the front tends to continue straight ahead in a bend), the brakes will be applied on the inside rear wheel. If the car starts to over steer (the rear tends to drift out), the system will apply the brakes on the outside wheels until the measured and the calculated yaw rates correspond.
TRACTION CONTROL PROBLEMS
[95, 93 98-03, 9000, 900 94-98]
When the traction control system on Saabs fail they typically go into limp home mode. Limp home mode causes the car to work only in a dimished power capacity. The name actually says it all. This mode will enable you to get home but that is about all. The car will only run about 30 MPH or so.
Most of the traction control failures can be attributed to the traction control throttle body potentiometer failing. You can only replace the throttle body itself when this happens as they are sold as a complete unit. Installation of a new unit is easy but should be done by authorized Saab dealer. The TCS system will have to be reset with the Saab tool to work correctly.
Saab 9000 only – The Saab 9000 started the Traction Control Frenzy but was really a tough system to diagnose when failing because of the system variables. Common problems were the throttle body, safety valve and pedal potentiometer. Truth is, if you are not very skilled and have the Saab Isat scan tool (for diagnostic purposes) then you are better off letting someone work on this system that has experience.