With the Examiner in voltmeter mode, select an end of scale of 20 Volts and a time base of 5 seconds

Connect the black probe of an Examiner to the vehicle earth and the red probe to pin 3 of the sensor output signal

Turn the ignition key to the ON position

Wait about 36 secs for the sensor to warm up

Spray the suitable gas required to activate the sensor within and not after 60 seconds

Press the START button.

The signal shown should be a set of PWM impulses with a frequency of 5 Hz and a Duty Cycle that varies between 20 and 60% as indicated in the table below.

PWM% Duty Cycle = T1 / T2 where:

· T1= duration of impulse

· T2 = 1/f = 1/5 Hz = Duration of transmission

Pin out:

· 1. +CH/15

· 2. earth

· 3. output signal

· 4. not connected

PWM signal meaning

0% short circuit to earth of signal line

20% non polluted air circulation

40% level 1 pollution

50% level 2 pollution

60% level 3 pollution

80% Sensor error

100% short circuit +12 signal line