Checking the vehicle speed sensor (VW Lt 2d)

1. Connect the VAG 1551 tester and, by entering "01" "Engine electronics", select the engine control unit. The engine should be idling. The display should show the following information:

• Fast data exchange HELP
• Dial function XX

2. Press "08" to select the "Read Block of Measured Values" function and confirm with the "Q" button. The display should show the following information:

• Reading the measured value block HELP
• Enter group number XX

3. Press "0" and "06" to select the "Display Group 06" function and press "Q". Perform the test and compare the readings on the display and on the speedometer.

• Reading measured value block 6 →
• 55 km/h 0 0 0 00000 255

The specified value is displayed in field 1.

4. Press "→". Press "06" to select the "Quick Data Exchange" function and confirm by pressing the "Q" button.

5. Turn off the ignition.

On vehicles with a 68-pin control unit connector

6. If the voltage does not change, connect the VAG 1598/18 tester to the engine control unit wiring harness. Check the wire from pin 43 of the engine control unit connector to the instrument panel connector for an open or short circuit.

On vehicles with a 121-pin control unit connector

7. If the voltage does not change, connect the VAG 1598/31 tester to the engine control unit wiring harness. Check the wire from pin 20 of the engine control unit connector to the instrument panel connector for an open or short circuit.