Vehicle Speed Sensor: Testing and Inspection

Vehicle Speed Signal, Checking


NOTE:
- The vehicle speed signal is generated by the speedometer Vehicle Speed Sensor (VSS) -G22- (at transmission) and is processed in the instrument cluster.
- The processed signal enters at terminal 54 of the ECM and is used for idle stabilization and tip-in shock reduction during shifting.


Test requirement:
- Function and display of speedometer OK.
Troubleshooting:

Test sequence
- Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word". Engine must run at idle. Refer to "Testing and Inspection


WARNING!
To reduce the risk of accident during road tests, always observe safety precautions.


When indicated on display


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -8- to select "Read Measuring Value Block" and press -Q- button to confirm input.

When indicated on display


Read measuring value block Q
Enter display group number XXX


- Press buttons -0-, -0- and -5- to select "display group number 005" and press -Q- button to confirm input.

Indicated on display


Read Measuring Value Block 5 ->
1 2 3 4


Determining via road test whether vehicle speed is displayed in display field 3.

- If vehicle speed is not display, lift vehicle -if possible using a vehicle lift-until front left wheel is free.
- Connect VAG1598/31 test box at wiring harness to Engine Control Module (ECM), do not connect ECM. Refer to "Scan Tool Testing/Wiring and Component Testing Using VAG1598/31 Test Box", Testing and Inspection
- Connect VAG1527B voltage tester to sockets 3 (B+) and 54 (VSS) of VAG1598/31 test box.
- Switch ignition on and turn front left wheel by hand.
- LED must blink (very brief blink signal).

If LED does not blink:
- Check following wire connection for open circuit and short circuit to Ground (GND) and B+:

Test box VAG1598/31 Instrument cluster
Socket Terminal
54

- Repair open circuit or short circuit if necessary.