Vehicle Speed Sensor Checking: Notes

NOTE: All voltage and continuity tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated differently in testing procedures. For help with diagnostic testing. See WIRING DIAGRAMS .

NOTE: The Vehicle Speed Sensor (VSS G68) sends a speed signal to the Engine Control Module (ECM). If speed signal fails, Engine Speed (RPM) will be limited to 5320 RPM within 4 seconds, at full load.

For the following fault to be entered into Diagnostic Trouble Code (DTC) memory: "00281 Vehicle speed sensor -G68- no signal" an engine speed of 4000 RPM must be maintained or exceeded for 4 seconds, at full load.

Location of Vehicle Speed sensor (VSS) and harness connection. See COMPONENT LOCATIONS .

This speed signal initiates the following control functions:

Gear recognition (i.e. for A/C compressor cut-out in first gear).
IDLE-to-DRIVE switch-over (i.e. for automatic transmissions, at speeds over 2.5 MPH).
Automatic transmission protection (i.e. under 12.5 MPH, stall speed drops to 2900 RPM after 4 seconds).
Speed limiting (i.e. at 2130 MPH).