Traction Control System For Manual Gear Box

The main function of the TCS system is to regulate and control the position of the throttle butterfly valve in the throttle body. As it does this electronically, it is called the Electronic Throttle System, ETS.

Apart from control module 376, the system consists of a comparatively small number of components.

Throttle body 378 is equipped with a motor for regulating the throttle butterfly valve, a vacuum unit, a throttle position sensor and a safety cut-out.

Mounted on the accelerator pedal is pedal position sensor 379 with a potentiometer which senses the current position of the accelerator pedal.

As a safety feature, there is also a parallel system with a throttle cable which is activated when driving in limp-home mode.

Data concerning vehicle speed is received by the control module from two different sources: from speed sensor 132 at the rear of the instrument and from TC-ABS electronic control module 382 (average of the two front wheels). By comparing these signals and indicating faults when there is any deviation, we can check that both systems are working and in this way achieve a high degree of safety.

Data concerning engine speed is received by the ETS throttle control module from Trionic control module 430, which in its turn receives data on engine speed from the crankshaft position sensor on the belt pulley.

This information is used, among other things, for temperature dependent engine speed control which the system uses after starting.

The engine load signal (Tq) from Trionic control module 430 is a measure to the intake mass air flow. This information is used by the ETS system when driving with the Cruise Control on, and to detect when fuel shut-off occurs.

The brake pedal switch is activated as soon as the brake pedal is touched and breaks the Cruise Control connection (breaking contact).

An NTC resistor (202) is used to provide data about the engine temperature (coolant temperature). This data is used, among other things, to regulate the increase in engine speed after starting from cold.

The function of boost pressure control valve 381 is to disconnect the turbo charge air bypass valve when the car is driven with the Cruise Control system engaged or during antispin control. This prevents the charge air bypass valve fluctuating between the open and closed positions and causing variations in boost pressure and speed.

Operating current for main relay 377 is grounded via control module pin 13, which activates the relay and supplies the system with current (+30 circuit). When safety-related faults arise in the system, the grounding connection on pin 13 is broken, deactivating the relay and breaking the supply of current via the +30 circuit. When this happens, the current supplied to safety valve 380 on the bulkhead partition is also cut off, causing the valve to close the vacuum hose between the intake manifold and the throttle body's vacuum chamber. When the vacuum in the throttle body disappears, the throttle butterfly valve lever is moved back to the closed throttle position and the throttle cable is tensioned. In other words, the limp- home mode is engaged.

The ETS system communicates with the ISAT scan tool via data link connector 348.

Communication is in the form of a pulse train and enables the system to be cleared of any incorrect data in the system. It also enables command codes to be sent for activation of certain system functions, clearing of the system's DTC memory, etc..

When a fault occurs in the lets system which affects the performance of the system, the lamp circuit is grounded via pin 23 of the control module and warning lamp 47Y lights up.

To find out what fault has caused the warning lamp to light up, the ISAT scan tool must be connected to the data link connector and scan tool diagnostics undertaken.