LL2 Check Front Left Speed Sensor Output

- Lower vehicle so that wheels are just far enough off the ground to permit all wheels to turn.

- Remove left front wheel. Knock back the front disc brake caliper (2B121) so that the wheel can move as freely as possible. Remount the wheel

- Place in 4x4 low mode. Start engine and allow wheels to spin and stabilize at engine idle speed.

NOTE: Perform the following measurements with Rotunda(r) 105-00053 Digital/Analog Volt-Ohmmeter or equivalent. If not using Rotunda(r) 105-00053 or Fluke(r) Frequency Meter, higher wheel speed may be required in order for the frequency meter to function correctly.

- Set the Rotunda(r) Digital/Analog Volt-Ohmmeter 105-00053 or equivalent, to the frequency counter (Hz) setting. Measure and record the frequency between Pins 24 and 25 on the Rotunda(r) Breakout Box 014-00322 or equivalent. Using the Breakout Box For Circuit Checks

- Change the meter to the A/C mV setting. Measure and record the voltage output between Pins 24 and 25 on the Rotunda(r) Breakout Box 014-00322 or equivalent.

NOTE: Measurements of both the frequency and the voltage output must be taken. The actual speed the wheels are turning is not important -- the result of voltage output divided by the frequency will not change with wheel speed. However, it is crucial that both the frequency measurement and the voltage measurement be taken at the SAME wheel speed.

- Determine the sensor output in mV/Hz - Output -- A/C Voltage/Frequency

- Is the sensor output greater than 3.0 mV/Hz?

YES -- Output at anti-lock brake control module indicates that the air gap and speed sensor strength are OK. Go to LL7. LL7 Check For Wiring Intermittents

NO -- Speed sensor output at anti-lock brake control module is insufficient. Go to LL3. LL3 Check Front Left Sensor Output at Speed Sensor