Code 44221, 24221, 2422A, 24251 or 24291

Cause Of Fault
Left front wheel sensor
- Defective sensor wheel, incorrect gap between sensor and sensor wheel, sensor not secured or incorrect bearing clearance in the wheel bearing.
- Faulty sensor signal to Electronic Control Unit (ECU), break in continuity/short- circuit in wires or winding.

Symptom
The ANTI LOCK light is lit.

Action
1. Raise the car.
2. With the ignition in the Drive position, enter command code 259 on the ISAT.
- 8B 0XX appears on the display (left front wheel speed) (XX = 0 - 20km/h), depending on whether the wheel is stationary or rotated by hand.
- With a multimeter set to AC, take a reading of the signal across pins 30 and 48.
It should be between 150 and 700 mV (AC)
- With the ignition turned off and the connector of the ECU removed, check the sensor winding for breaks in continuity by measuring the resistance between pins 30 and 48.
The resistance must be approx. 1 kohm.





- Also check the wires between the sensor and pins 30 and 48 of the Antilock Brake System (ABS) ECU for short-circuits and for poor contact in the connector.
Resistance to earth is measured as follows:
between pin 30 and earth, correct value = OL
between pin 48 and earth, correct value = OL
Voltage in the event of a short-circuit to + 12 V is measured as follows:
between pin 30 and earth, correct value = 0 Volts (DC)
between pin 48 and earth, correct value = 0 Volts (DC)
3. Check that the left front wheel sensor is firmly in position.
4. Check that the sensor wheel is not damaged and is firmly in position.
- Check also that there is no bearing clearance.
5. Check the gap between the sensor and sensor wheel.
- The gap must be 0.65 mm.
6. Check that the ECU has a satisfactory earth connection at pin 1 and pin 19.
7. If no fault is discovered, test-drive the car and check whether the trouble code is triggered again.
- If so, see Actions Before Replacing ECU