NN2 Check Rear Axle Speed Sensor Output at ABS Module

NN2 CHECK THE REAR AXLE SPEED SENSOR OUTPUT AT THE ANTI-LOCK ELECTRONIC CONTROL MODULE

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

- Start the engine and allow the rear wheels to spin and stabilize at engine idle.

NOTE: Perform the following measurements with a digital/analog volt-ohmmeter with a frequency meter.

- Set the meter to the frequency counter (Hz) setting. Measure and record the frequency between Pins 21 and 22 on the breakout box.

- Change the meter to the A/C mV setting. Measure and record the voltage output between Pins 21 and 22 on the breakout box or equivalent.

- Determine the speed sensor output in mV/Hz:
Output - A/C voltage/frequency

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 the voltage output divided by the frequency will not change with the wheel speed. However, it is crucial that both the frequency measurement and the voltage measurement be taken at the same wheel speed.

Is the sensor output greater than 6.0 mV/Hz?

> Yes
Output at the ABS control module indicates that the air gap and sensor strength are OK. Go to Pinpoint Test NN4. NN4 Check For Wiring Intermittents

> No
Sensor output at the ECU is insufficient. Go to Pinpoint Test NN3. NN3 Check Rear Axle Sensor Output at Speed Sensor