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Code 21, Left Front Speed Sensor

  1. Turn ignition off. Unplug ABS/AWD control unit. Using a DVOM, measure speed sensor resistance between pins No. 48 and 51 of ABS/AWD control unit wiring harness. Sensor resistance should be 600-1600 ohms.
  2. If resistance is incorrect, check wiring harness between ABS/AWD control unit and left front speed sensor (including pins/connectors). If circuit is okay, replace speed sensor.
  3. If resistance is correct, check speed sensor voltage signal at plug (on spring strut mount in trunk). See Figure . Connect oscilloscope to speed sensor side.
  4. Depending on oscilloscope, select special input or secondary image 6display. Turn left front wheel by hand at about one revolution per second.
  5. Oscilloscope should display of 2 volts, as measured peak to peak. If voltage signal is incorrect, ensure speed sensor air gap is correct. Ensure wheel bearing or pulse wheel is not damaged or corroded. Repair as necessary.
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