The Vehicle Speed Sensor (VSS) is a small signal generator that is turned by a gear inside the transmission assembly. The Vehicle Speed Sensor produces 8 pulse per rotation which a stock computer assumes 8000 pulses per mile. The Vehicle Speed Sensor (VSS) is a variable reluctance sensor that generates a waveform with a frequency that is proportional to vehicle road speed. When the vehicle is moving slowly, the sensor produces a low frequency signal. As the vehicle speed increases, the sensor produces a higher frequency signal The Vehicle Speed Sensor (VSS) supplies this signal to the components that require vehicle speed information including the speed control amplifier for cruise control equipped vehicles and computer. The computer uses the VSS signal for emmisions contol programs and speed limiters. The emmisions programing can cause a manual transmission vehicle to stall out while decelerating if no VSS is used.
The VSS is a magnetic pickup normaly mounted in the transmission like a speedo cable.
The Vss is used mostly for cruise control but some people have had problems with hard stops when not useing one. It also controls the Idle Speed Control (ISC), Transmissinn torque lock and the engine cooling fan.
Set the Y values to Zero in the Desired Idle AF In Drive function, anytime the EEC is seeing a possitive signal from the VSS it uses this table and compares it to the MAF Xfer to control idle, if you find the Idle drops too fast or low then slowly increase the values until it's right.
Should look like this OEM:
( 1.04856e+06, 2.03662 ) ( 1504, 2.03662 ) ( 1120, 1.49365 )
( 816, 1.05762 ) ( 704, 0.898926 ) ( 592, 0.73877 )
( 496, 0.602539 ) ( 0, 0 ) ( 0, 0 )
Adjust to this as a starting point:
( 1.04856e+06, 0.0) ( 1504, 0.0) ( 1120, 0.0)
( 816, 0.0 ) ( 704, 0.0) ( 592, 0.0)
( 496, 0.0) ( 0, 0 ) ( 0, 0 )
The VSS is used for the ISC. When the car is moving in excess of 6mph the RPM is held at about 1100 until the speed is reduced below
6mph. Then the idle will drop to 800 or so.
So if the VSS is disconnected and your idle is pretty low to begin with, the car may stalll upon
deceleration.
