Vehicle Speed Sensor: Testing and Inspection

CHECKING REQUIREMENTS:
- Speedometer in instrument cluster OK.

CHECKING:
- Using VAG 1551 scan tool, select "Read Measuring Value Block" function 08, display group 003.
- Indicated on display;

Read measuring value block 3
1 2 3 4

- Observe display field 4 while accelerating from standstill.

Specified Values:
- 0 mph (at standstill).
- Actual speed (vehicle driven).

- Press arrow button.
- Select "End Output" function 06.
- Press -Q- button to confirm input.

If no vehicle speed is displayed between standstill and moving:
- Switch ignition OFF and connect VAG 1598/19 test box.
- Connect VAG 15278 voltage tester between test box sockets 13C (signal) and 10D (B+).
- Raise front of vehicle until left-front wheel is free to rotate.

NOTE: The right front wheel must NOT rotate.

- Switch ignition ON.

Voltage tester must light up at half strength.

- Rotate left front wheel by hand.

Voltage tester must become brighter (flash).

If tester does not light up (become brighter) or flash:
- Check wiring between test box socket 13X and vehicle speed sensor, using wiring diagram.
- Find and eliminate open circuit in wiring between terminal C13 and vehicle speed sensor.

If wiring is OK:
- Replace vehicle speed sensor.

If voltage tester does not light up (become brighter) or flash:
- Replace ECM.