Speedometer Vehicle Speed Signal, Checking

Speedometer 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.

Requirement
- Function and display of speedometer OK. Troubleshooting

Work sequence

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

- Connect VAS5051 tester, Vehicle Diagnostic, Testing and Information System VAS 5051, Connecting and Selecting Functions and select vehicle system "01 - Engine electronics". Engine must run at idle.







Display on VAS5051:
- Select diagnostic function "08 - read measured value block" in selection -1-.







Display on VAS5051:
1 - Enter display group. Max. input value = 255
- Select function "005" in button field -2- for "display group number 005" and press Q button to confirm input.







Display on VAS5051:
- Determine via road test whether vehicle speed is displayed in 3.
- If vehicle speed is not displayed, lift vehicle - if possible using a vehicle lift - until front front wheel is free.
- Connect VAG1598/31 test box at wiring harness to Engine Control Module (ECM) but do not connect ECM. Scan Tool Testing and Procedures
- Connect VAG1527B voltage tester to sockets 3 (B+) and 54 (VSS) of VAG1598/31 test box.
- Switch ignition on and turn left front wheel by hand.
- LED must blink (very brief blink signal).

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

Test box VAG1598/31 Socket Instrument cluster Terminal
54 Electrical Wiring Diagrams, Troubleshooting & Component Locations

- Repair open circuit in wiring or short circuit if necessary.