Test Description
EBCM/EBTCM performs 2 basic checks on wheel speed sensors: sensor continuity and sensor output. When ignition switch is first turned to RUN position, EBCM/EBTCM performs wheel speed sensor continuity check. Any condition causing lack of continuity in front wheel speed sensor circuit could result in setting of DTC 21 or 25. Conditions include the following: open or short to ground, short between 2 wheel speed sensor circuits, short in wiring harness between speed sensor and EBCM/EBTCM, or open or short to ground across wheel speed sensor coil.
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Scheme 25
Toothed wheel generates a voltage pulse as it moves past sensor. EBCM/EBTCM uses these pulses to determine wheel speed. EBCM/EBTCM uses wheel speed sensor signal to calculate vehicle reference speeds, individual speed, acceleration value and slip value for each wheel. These values are used to determine when anti-lock or traction control (if equipped) is needed.
In order to prevent electromagnetic interference from disturbing wheel speed sensor signal, wiring from EBCM/EBTCM to each wheel speed sensor are twisted, in pairs, a minimum of 6-9 turns per foot. When servicing speed sensor wiring, maintain original wiring twists.
EBCM performs 2 basic checks on wheel speed sensors: sensor continuity and sensor output. When ignition switch is first turned to RUN position, EBCM/EBTCM performs wheel speed sensor continuity check.
Any condition causing lack of continuity in rear wheel speed sensor circuit could result in setting of DTCs 31 or 35. Conditions include the following: open or short to ground, short between 2 wheel speed sensor circuits, short in wiring harness between speed sensor and EBCM/EBTCM, or open or short to ground across wheel speed sensor coil.
Scheme 26
Scheme 27
Toothed wheel generates a voltage pulse as it moves past sensor. EBCM/EBTCM uses these pulses to determine wheel speed. EBCM/EBTCM uses wheel speed sensor signal to calculate vehicle reference speeds, individual speed, acceleration value and slip value for each wheel. These values are used to determine when anti-lock or traction control (if equipped) is needed.
In order to prevent electromagnetic interference from disturbing wheel speed sensor signal, wiring from EBCM/EBTCM to each wheel speed sensor are twisted in pairs, a minimum of 6-9 turns per foot. When servicing speed sensor wiring, maintain original wiring twists.
DTC 22, 26, 33 or 36 will set if EBCM/EBTCM detects electromagnetic interference in a wheel speed sensor signal. Possible interference sources include accessory motors, wiper motors, ignition circuit and add-on or aftermarket equipment.
DTC 22, 26, 32 or 36 will set if EBCM/EBTCM determines wheel speed signal is erratic; for example, wheel speed signal indicates wheel is accelerating or decelerating faster than physically possible. An intermittent open or short to ground in a wheel speed sensor could also set DTC.
DTC 23, 27, 33 or 37 will set if EBCM/EBTCM does not sense any wheel speed signal, but determines continuity exists in speed sensor circuit. No wheel speed signal could be caused by a dislodged wheel speed sensor, missing toothed sensor ring (front) or defective hub/bearing assembly (rear).
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When ignition switch is first turned to RUN position, EBCM/EBTCM goes through a self-check, which lasts 2-4 seconds. During self-check, EBCM/EBTCM grounds terminal No. 34 to energize main relay. After self-check is completed, main relay remains energized.
With main relay energized, battery voltage is delivered to EBCM/EBTCM and Pressure Modulator Valve (PMV) during vehicle operation. Constant battery voltage allows vehicle to enter ABS mode without delay. If Amber ANTI-LOCK warning light comes on because of a system fault, main relay will be de-energized, causing ABS system to shut down.
If battery voltage is not detected at PMV or EBCM terminals No. 3, 20, and 33, DTC 45 will set when ignition switch turned to RUN position. DTC 45 will also set if EBCM detects an open or a short to ground in left inlet valve circuit.
Check for open in circuit No. 342 (Red wire), circuit No. 641 (Brown wire), circuit No. 1632 (Pink wire) and circuit No. 1633 (Red wire). Check main relay for open circuit. (Scheme 1) Check for short to ground in circuit No. 342 (Red wire), circuit No. 858 (Dark Green/Yellow wire) and circuit No. 1633 (Red wire).
