FixVault
Home › Subaru › 1995 › Legacy Base › Repair and Diagnosis › Brakes › Traction Control › Anti-Lock Brake System - Except 5.3 Abs Or Abs/TCS › Testing › Test 1: Open Wheel Speed Sensor Or Circuit

Test 1: Open Wheel Speed Sensor Or Circuit

  1. Turn ignition off. Disconnect ABS control unit harness connector. Depending on specific trouble code, check resistance between ABS control unit harness connector terminals. See CHECKING CONTROL UNIT RESISTANCE  table. See Figure . Resistance should be 800-1200 ohms.
  2. Check resistance between ABS control unit harness connector terminals and ground. See CHECKING CONTROL UNIT CONTINUITY  table. Resistance should be infinite. Turn ignition on. Using voltmeter, measure voltage between ABS control unit harness connector terminals and ground. See CHECKING CONTROL UNIT VOLTAGE  table. Voltage should be zero volts. If resistance and voltage checks are as specified, go to next step. If measurements are not as specified, go to step 6).
    CHECKING CONTROL UNIT RESISTANCE

    DTC (1) Terminals No.
    21 21 & 23
    23 4 & 22
    25 24 & 26
    27 8 & 9
    (1) Using ohmmeter, check resistance between specified terminals.
    CHECKING CONTROL UNIT CONTINUITY

    DTC (1) Terminal No.
    21 23
    23 22
    25 24
    27 8
    (1) Using ohmmeter, check resistance between specified terminal and ground.
    CHECKING CONTROL UNIT VOLTAGE

    DTC (1) Terminals No.
    21 23
    23 22
    25 24
    27 8
    (1) Using voltmeter, measure voltage between specified terminal and ground.
  3. Turn ignition off. Raise and support vehicle. Ensure ABS control unit harness connector is disconnected. Remove harness connector back cover. Connect harness connector to ABS control unit. Turn ignition on. Using oscilloscope, check wheel sensors voltage input (waveform).
    NOTE: After completing inspection of sensors, clear memory of control unit. DTC 29 may be stored due to test.
  4. Backprobe control unit connector with oscilloscope test probes. See Figure . Rotate each wheel depending on trouble code. Connect probes to selected terminals. See CHECKING WHEEL SENSOR INPUT VOLTAGE table. Voltage should be .12-1.00 volt (AC waveform). If input voltage is not as specified or waveform is erratic, go to next step. If input voltage is as specified and waveform is not erratic, replace ABS control unit.
    CHECKING WHEEL SENSOR INPUT VOLTAGE

    DTC (1) Terminals No.
    21 21 & 23
    23 4 & 22
    25 24 & 26
    27 8 & 9
    (1) Use oscilloscope to measure voltage between specified terminals.
  5. Inspect wheel speed sensor air gap. See WHEEL SPEED SENSOR AIR GAP  under ADJUSTMENTS. Adjust as necessary. Ensure sensor(s) are not damaged. If sensor adjustment is as specified and no damage is present, go to next step.
  6. Check resistance of wheel sensors. Disconnect wheel sensor harness connector. Using ohmmeter, check resistance between sensor connector terminals. Resistance should be 800-1200 ohms. If resistance is not as specified, replace wheel sensor. If sensor resistance is as specified, inspect and repair circuit(s) between sensor and ABS control unit. See WIRING DIAGRAMS  .
About FixVault