Test 3: Wheel Speed Sensor Problem

NOTE: Code 29 may be set when vehicle is towed, wheels are raised and spun or vehicle is driven with steering at full lock.

Inspect size and condition of tires. Ensure tires are correct size. See tire placard under driver's door latch. If individual tire is unevenly worn compared to other tires on vehicle, DTC may be set. Replace tire(s) as necessary.
Ensure ignition is off. Raise and support vehicle. Disconnect ABS control unit harness connector. 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.

Backprobe control unit connector with oscilloscope test probes. See Figure . Rotate appropriate wheel depending on trouble code. Connect probes to appropriate terminals. See CHECKING WHEEL SENSOR INPUT VOLTAGE table. Voltage should be .12-1.00 volt (20 hz 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

Wheel Sensor

⁽¹⁾ Terminals No.

Right Front

23 & 21

Left Front

22 & 4

Right Rear

24 & 26

Left Rear

8 & 9

⁽¹⁾	Using voltmeter, measure voltage between specified terminals.

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, go to next step.
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, replace wheel sensor.