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Speed, lead from ABS

Speed, lead from ABS



The ABS control module sends a speed signal to pin 64 of the Trionic T7 control module. The signal is a square wave that varies between 0 V and B+ 29 times per wheel rotation. This speed signal is used to:


• prevent adaptation of idle speed control when the car is moving.

• on manual gearboxes, determine which gear is currently being used. This makes it possible to limit torque in gears R and 1 and activate fuel shut-off in gears 2, 3, 4 and 5. Control of the SHIFT UP lamp also depends on the current gear.

• activate speed limitation by limiting the maximum air mass/combustion at 240 km/h.




Diagnostics


• If there is no speed signal, diagnostic trouble code P0502 will be generated.

• If the speed value is implausible, diagnostic trouble code P0501 will be generated.


System reaction to a fault


• The speed (bus from MIU) is used as a substitute value.

• Cruise control is blocked.