Test H EBCM/EBTCM/Wheel Speed Circuit Input Test

H: EBCM/EBTCM/Wheel Speed Circuit Input Test:

ABS/TCS:

OPERATION:
^ When each wheel turns, the wheel speed sensor creates a small AC voltage with a frequency proportional to wheel speed. This magnetically induced voltage is caused by a toothed sensor ring passing the wheel speed sensor's stationary pickup coil. The toothed sensor ring is mounted on the drive axle in the front, and the hub/bearing assembly in the rear.
^ The EBCM/EBTCM uses the wheel speed sensor signal to calculate vehicle reference speeds, and individual wheel speed, acceleration and slip values. These values are used to determine when antilock control is required. Vehicles equipped with traction control also use front wheel speed sensor signals to determine when traction control is required.
^ To prevent electromagnetic interference from disturbing the wheel speed sensor signal, the cables from the EBCM/EBTCM to each wheel speed sensor are twisted in pairs a minimum of 6 to 9 turns per foot. When servicing the sensor cables, it is important to maintain the original cables' twists (6 to 9 turns per foot).
^ DTC 22, 26, 32, or 36 sets when the EBCM/EBTCM determines that a wheel speed signal is erratic. A wheel speed signal indicating that a wheel is accelerating or decelerating taster than physically possible is an example of an erratic signal. An intermittent open or short to ground in a wheel speed sensor could also cause the EBCM/EBTCM to set a diagnostic trouble code. DTC 22, 26, 32, or 36 also sets when the EBCM/EBTCM detects electromagnetic interference (noise) in a wheel speed sensor signal. Possible interference sources include accessory motors, wiper motors and ignition circuits.
^ DTC 23, 27, 33 or 37 sets when the EBCM/EBTCM does not see any wheel speed sensor signal, but determines that continuity exists in the circuit. This is caused by a dislodged wheel speed sensor, missing toothed sensor ring (front) or defective hub and bearing assembly (rear).
^ Any condition which would result in lack of continuity in a wheel speed sensor circuit could result in DTC 21 or 25 (front) or 31 or 35 (rear) being set. These conditions include an open, a short to ground, or a short between the two wheel speed sensor circuits in the wiring harness between the speed sensor and EBCM/EBTCM. Also, an open or short to ground across the wheel speed sensor coil could trigger this diagnostic trouble code.

POSSIBLE CAUSES:
- Faulty or dislodged wheel speed sensor.
- Missing or irregular toothed sensor ring.
- Open or short to ground in wheel speed sensor circuit.
- Short between wheel speed sensor circuits.
- Erratic wheel speed signal.
- Defective hub and bearing assembly.
- Intermittent open or short to ground in wheel speed sensor circuit.
- Noise interference in wheel speed sensor signal.
- Improperly twisted sensor cable.