Speed Signal

The ABS electronic control module sends a speed signal to pin 39 of the Trionic engine control module. This signal is a square wave which varies between 0 V and B+ 29 times per wheel revolution. This speed signal is used to:

^ determine which gear is engaged at the time
^ activate the SHIFT UP lamp (does not apply to 5th gear)
^ limit the boost pressure in Reverse, 1st and 2nd gears
^ activate fuel shut-off in 3rd, 4th and 5th gears
^ activate speed limitation (by limiting the boost pressure at 230 km/h)
^ prevent adaptation of idle speed control when the car is in motion. In the absence of a speed signal the above functions are not performed and, on cars with a manual gearbox, boost pressure is limited.