3
Diagnostics, Troubleshooting and Testing
23
WABCO
Maintenance Manual MM-0112 (Revised 07-18)
Testing
Wheel Speed Sensor Testing
Sensor Adjustment
앫
Push the sensor in until it contacts the tooth wheel.
앫
Do not pry or push sensors with sharp objects.
앫
Sensors will self-adjust during wheel rotation.
Electrical Checks
앫
Check wheel speed sensor by itself for resistance.
앫
Check ECU harness and sensor together for resistance.
Figure 3.14 and Figure 3.15.
앫
Verify no change in resistance or open circuit between sensor by
itself and through harness.
앫
Check harness by itself for any shorts to battery and shorts to
ground.
앫
Measurements should read as follows:
NOTE:
Sensor resistance can change with temperature. All
readings should be taken at the same time and before vehicle is
driven.
7 System function
1 J1939 or proprietary ESC CAN. Several sensors out of adjustment
2 ATC 3/2 valve
3 Retarder relay or third brake relay such as drive line brake, exhaust brake or
engine brake
4 ABS indicator lamp
5 ATC configuration
6
Trailer active braking valve or front axle active braking valve
7 Brake pressure sensor
8 Tire pressure monitoring
8 ECU
1 Low power supply
2 High power supply
3 Internal fault
4 System configuration error
5 Ground
6
RSC accelerometer or ESC module
First Digit (Type of Fault)
Second Digit — Specific Location of Fault
Location
Measurement
Between sensor leads
900-2000 ohm
At ECU harness pins with sensor
connected
Same as above, no more than 1
ohm difference
ECU harness by itself for DC
voltage or ground
No continuity
Sensor output voltage
At least 0.2 volt AC at 30 rpm
