Circuit Description

Vehicle Speed Sensor (VSS) is a hall effect type sensor that interacts with magnetic field created by a rotating magnet attached to and rotated by transmission output shaft. Meter fuse supplies 12 volts to VSS hall sender circuit. VSS pulses a 9-volt signal sent on reference circuit from ECM to ground. ECM interprets vehicle speed by monitoring number of pulses to ground on reference circuit.

When DTC sets, ECM illuminates MIL on second trip after fault was detected. ECM will store conditions present when DTC was set as freeze frame data in the FAILURE RECORDS data.

ECM will turn MIL off on third consecutive trip cycle during which diagnostic runs and fault is no longer recognized. A history DTC will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to ECM.