Test 03 - Dynamic Speed Sensor Test

TEST SEQUENCE
1. Connections needed:
- T-plug (4a) with adapter (A) at Antilock Brake System (ABS) wire harness (1)
- T-plug (4b) at ABS control unit (2)
- Connecting lead at adapter (A) to cigarette lighter - red telltale lamp comes "On"
2. Switch position at adapter (A), on '7' model and test step 03 (left).
3. Raise car and turn wheels at steady speeds within nominal periods approx. 5km/h (3 mph) until 100% display appears.





Nominal Values

4. Compare the displayed actual values obtained from the test equipment with the nominal values provided above. If nominal values are not obtained, proceed with the troubleshooting procedures below as needed.

TROUBLESHOOTING

NOTE: Wire harness and control unit connected.

Speed Sensors (DF)
Cycle Time
- Cycle time < specified value: wheel turns too fast
- Cycle time > specified value: wheel turns too slow

Visual Inspection
- Excessive clearance between speed sensor end pulse wheel. Speed sensor loose or dirty; check installation.
- Check arrangement of wheel with gauge. Hold opposite wheel on rear axle. Replace speed sensor.

Pulse
- Gear rotation not uniform enough. Check pulse wheel teeth (condition, dirt).
- Check clearance between speed sensor and pulse wheel.
Replace pulse wheel.





Oscilloscope Test
The speed sensor pulses can also be checked individually with the BMW Service Tester Oscilloscope. Connection with universal adapter at wire harness connector.

Turn corresponding wheel. The curve on the oscilloscope increases as the wheel speed increases. Ensure uniformity between shafts.