Traction Control System: Description
Saab Traction Control System (TCS) operates in tandem with appropriate Anti-lock Braking (ABS) system. Saab 9000 series vehicles are equipped with Mark IV ABS. TCS is made up of 2 subsystems: ABS and Electronic Throttle System (ETS). System also incorporates a cruise control function. An additional Automatic Slip Reduction (ASR) system is used on automatic transmission models.
TCS uses many components already included in ABS system, including wheel sensors, hydraulic unit and valve block. TCS system consists of 2 different variations, one for manual transmission and one for automatic transmission. See Fig 1 and Fig 2 .
Manual transmission TCS has capability to apply front brakes independently during low speed wheel spin and also close throttle valve to reduce wheel spin at any speed. Automatic transmission TCS does not have capability to apply brakes during wheel spin conditions. Automatic transmission TCS does control operation of transmission kickdown cable in addition to controlling throttle valve. ABS components of system include a 55-terminal ECU (located on battery shelf), ABS hydraulic unit (with traction control valve block on manual transmission version), wheel speed sensors, and warning lights. See Fig 3.
Electronic Throttle System (ETS) utilizes a throttle cable only as an emergency limp-home measure, as it is an electronic (as opposed to mechanical) throttle operating system. Throttle is operated by a Pulse-Width Modulated (PWM) DC motor. ETS/ECU is located under driver's seat. See Fig 4.
ETS components of system include a 38-pin ECU, throttle housing assembly, pedal potentiometer, and solenoid valves. ETS ECU is identical for both manual and automatic transmission versions. If a new ECU is installed, it must be calibrated in order to identify which version car it is being used on.
Automatic Slip Reduction (ASR) components of system include 25-pin ECU and Kickdown Wire (KDW) motor. See Fig 5. ASR ECU is located on ETS ECU, under driver's seat. See Fig 6. ASR system operates in much the same way as manual transmission version, except it is much more sensitive. Generally, the driver is not aware of its operation other than that the TCS light is on.