Vehicle Speed Sensor: Testing and Inspection
Vehicle Speed Sensor (VSS) signal, checking
NOTE:
- The vehicle speed sensor is generated by the Vehicle Speed Sensor (VSS) -G68 at the transmission and processed in the instrument cluster.
- The processed signal is received at terminal 54 by the Engine Control Module (ECM) and is used for idle stabilization and load change damping during gear shift change.
- Connect Vehicle Diagnostic, Testing and Information System VAS5051 or VAG 1551 Scan Tool and select engine electronics control module by entering address word "01", Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1551/ VAS 5051 Scan Tool" Testing and Inspection . When doing this the ignition must be switched on.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select function "Read Measuring Value Block" and confirm entry with -Q- button.
Indicated on display
Read Measuring Value Block
Input display group number XXX
- Press buttons -0-, -0- and -5- to select "display Group number 005" and confirm entry with -Q- button.
Indicated on display
Read Measuring Value Block 5 ->
1 2 3 4
- Perform road test.
WARNING!
- When driving or riding in an airbag equipped vehicle NEVER hold the scan tool or other test equipment in your hands or lap while in motion. Objects between you and the airbag increase the risk of injury in an accident.
- During a test drive in an airbag equipped vehicle, test equipment must always be fastened to and operated from the rear seat by a second technician. Please observe safety precaution.
- Checking specification for vehicle speed
Display Group 005: Vehicle Speed:
If vehicle speed is not displayed.
- Connect VAG 1598/31 test box to wiring harness for engine control module. DO NOT connect to engine control module itself, Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1598/31 Test Box" Testing and Inspection
The following wiring connection is to be checked for short circuit to B+, short circuit to Ground (GND) and an open circuit.
VAG 1598/31 Instrument cluster,
test box socket terminal
54
Wiring resistance: max. 1.5 Ohm
If no malfunction is identified in the wiring:
- Determine all "Users" of the vehicle speed signal (e.g. Radio, Automatic Transmission, Climate Control etc.) disconnect in sequence their connection to the instrument cluster and repeat test until cause is determined.
- Display readiness code, Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Displaying Readiness Code" Testing and Inspection . Readiness code must be generated if DTC memory was erased, Refer to "Monitors, Trips and/or Drive Cycle (Readiness Codes)/Generating Readiness Code" Testing and Inspection