Vehicle Speed Sensor: Testing and Inspection
Vehicle Speed Signal, Checking
Special Tools and Equipment
- VAG1526A
- VAG1527B
- VAG1594A
- VAG1598/31
- VAS5051 with VAG5051/1
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
WARNING!
To reduce the risk of accident during road tests, always observe safety precautions.
- Connect VAS5051 tester and select vehicle system "01 - Engine electronics". Engine must run at idle for this. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAS 5051 Tester, Connecting and Selecting Functions" Testing and Inspection
Display on VAS5051:
- Select diagnostic function "08 - Read Measuring 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:
- 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/Wire 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 the following wire connection for open circuit and short circuit to Ground (GND) and B+:
Test box Instrument cluster
VAG1598/31 Terminal
Socket
54 -
- Repair open circuit or short circuit if necessary.