PRE-RELEASE
Wheel-speed signal output
| Wheel-speed signal output |
Several other systems in the car need to know the wheel speed. The TC/ABS control module, which is connected to the P-bus, sends out information about the speed of all wheels. These speeds are based on the circumference of the wheels being 200 cm.
This information is processed in the main instrument unit into vehicle speed in km/h (mph). The speed is corrected to the tyre size that has been programmed. This vehicle speed is then sent out over the I-bus.
Wheel speed information is sent to systems that cannot handle bus information via pins 23 and 26.
The engine management system is connected to the P-bus and therefore has access to the same speed information.
Speed information can be sent even when the ABS, foot brake, ESP OFF or central warning lamps are on. The information is sent as long as one of the rear wheel sensors is working and the control module is working and supplied with power.
For more information on wheel speed on the bus, see Electrical systems, Bus and diagnostic communication,
System overview
and Main instrument unit,
System overview
.
