Faulty Wheel Speed Sensor Output
- Disconnect wheel speed sensor connector of sensor which set trouble code. See TROUBLE CODES table under SELF-DIAGNOSTICS. Test sensor. See WHEEL SPEED SENSOR under DIAGNOSIS & TESTING. If sensor is within specification, go to next step. If sensor is not within specification, replace sensor. See WHEEL SPEED SENSOR under REMOVAL & INSTALLATION.
- Check wheel speed sensor-to-rotor gap. See WHEEL SPEED SENSOR under ADJUSTMENTS. If wheel speed sensor-to-rotor gap is within specification, go to next step. If gap is not within specification, adjust sensor-to-rotor gap.
- Inspect wheel speed sensor rotor which set trouble code for damaged or missing teeth. If rotor is okay, go to next step. If rotor is damaged, replace rotor.
- Raise and support vehicle. Ensure ignition switch is in OFF position. Disconnect ECM connector. Install Adapter Harness (MB991356) to ECM chassis harness connector. See Fig 1
. DO NOT connect adapter harness to ECM except when recording waveform during test drive (optional). Connect DVOM or oscilloscope to terminals as specified. See TESTING WHEEL SPEED SENSOR OUTPUT table. Manually turn wheel to be measured at a rate of 1/2-1 turn per second. Observe DVOM or oscilloscope.TESTING WHEEL SPEED SENSOR OUTPUT
Application (1) Measure Between Terminals: Front Left Wheel Speed Sensor 4 & 5 Front Right Wheel Speed Sensor 21 & 23 Right Rear Wheel Speed Sensor 24 & 26 Left Rear Wheel Speed Sensor 8 & 9 (1) To identify adapter harness connector terminals, See Fig 1 . - If measurement is made with DVOM, more than 70 millivolts should be present. If measurement is made with an oscilloscope, more than 100 millivolts should be present and waveform should be as shown. See Fig 2 . If voltage output is low or no voltage output exists, test wheel speed sensor. See WHEEL SPEED SENSOR under DIAGNOSIS & TESTING . Replace or repair as necessary.
- Using an oscilloscope, observe waveform for each wheel with engine idling and transmission in low gear (on FWD, rear wheels must by rotated by hand). Output voltage is low when wheel speed is low and increases as wheel speed increases. If oscilloscope waveform is distorted or sensor voltage output is not within specification, go to next step. If oscilloscope waveform is normal and output voltage is within specification, go to step 8).
- Check for broken or disconnected wheel speed sensor wire, faulty wheel speed sensor installation and damaged wheel speed sensor rotor. If voltage is low or no voltage output exists, test wheel speed sensor. See WHEEL SPEED SENSOR under DIAGNOSIS & TESTING. Replace or repair as necessary.
- If no fault can be found with wheel speed sensor, wheel speed rotor or wiring harness, wheel speed sensor circuit is okay. Replace faulty ECM, clear codes and road test vehicle.