850 T-5 L5-2.3L Turbo VIN 58 B5234T5 (1997)
Speedometer Head: Description and Operation
Speedometer
Speedometer 12 Pulse Output
The speedometer is electronic and has a trip odometer. The speedometer receives a signal from the ABS control module which in turn receives a
signal from the front ABS sensors. The number of pulses per kilometer is 25,793 (41,500/mile) and corresponds to a tire circumference of 1,861
(6,102 ft) meters. The speedometer has two short-circuit proof outputs for the vehicle speed sensor (VSS) signal. One has the same frequency as the
input signal (48 pulses/revolution) and one has a frequency corresponding to 1/4 of the input signal: 12 pulses/revolution. The frequency of the
output vehicle speed sensor (VSS) signal is proportional to the frequency of the input signal and is used for the following systems:
Output, 12-pulse:
Ignition system
Fuel injection system
Cruise control
Audio
Output, 48-pulse:
Electronically controlled automatic gearbox.
Trip computer
ECC
It is important that accessories are connected to the output for the 12 pulse signal, see illustration. The incorrect connection of accessories can cause
speedometer failure and diagnostic trouble codes (DTCs) in the fuel, ignition or automatic transmission control systems.
