Checking Vehicle Speed Signal

CHECKING VEHICLE SPEED SIGNAL

REQUIREMENTS
^ Speed display in instrument cluster OK

PROCEDURE
- Connect VAG 1551 Scan Tool and initiate Read Measuring Block Value

NOTE:
See On-Board Diagnostics, "Read Measuring Value Block" function 08, display group 003, display field 4. Testing and Inspection

- Switch ignition on.
- Lift left front of vehicle until wheel is raised off of floor.
- Rotate left front wheel by hand.
^ Speed must be displayed on VAG 1551 scan tool

If NO speed is displayed:
- Switch ignition off and connect VAG 1598 test box with VAG 1598/11 adapter harness to ECM.
^ Adapter harness for ECM connector B is not connected.)

- Connect US 1115 LED tester or equivalent across test box sockets 29 (signal) and 40 (positive).
- Switch ignition on.
^ LED lights up at approx. half light intensity

- Turn left front wheel by hand.
^ LED lights up brighter and begins blinking

If LED does not light up and blink:

- Check wiring for continuity between test box socket 29 and instrument cluster, using wiring diagram.
- If necessary, eliminate break in wiring between ECM connector B terminal 9 and instrument cluster.
- If wiring is OK, procede to troubleshooting charts for Vehicle Speed Signal. Troubleshooting Charts

If LED lights up and blinks:
- Switch ignition off and connect connector -B- of VAG 1598/11 adapter harness to ECM.
- If necessary, re-connect LED voltage tester to test box sockets 29 (signal) and 40 (positive).
- Switch ignition ON.
^ LED must light up at approx. half light intensity

- Turn left front wheel slowly by hand.
^ LED must light up brighter and begin blinking

If NOT:
- Even though no malfunction was found with connector -B- not connected to ECM, Replace ECM.