4-14. O
2
Sensor
This is a very efficient method to check
and simulate O
2
Sensors.
This test hooks in parallel with the O
2
Sensor circuit. The primary display will
s how O
2
S ensor volt age, while t he
s ec ondary dis pl ay will show Cross
Counts (CC).
Cross Counts are the number of times
t he readi ng crosses 0. 45 V DC per
second.
Nominal CC is 1 to 3 for a good O
2
Sensor.
During this test, the secondary display
will indicate Full Lean, Lean, Rich, and
Full Rich respectively, according to the
measuri ng value of t he O
2
S e n s o r
output, together with the corresponding
Cross Counts(.x).
29
28
1. Set rotary selector to Elec position.
2. Press menukey 3 to select O
2
Sensor function.
“Lean” and “Rich” annunciators will be displayed on menu screen.
3. Insert black lead into COM terminal, red lead into Elec terminal, and green lead
into Signal terminal.
4. Unplug the O
2
Sensor connector.
5. Connect a jumper wire between the connector halves.
6. Connect red lead probe to the O
2
Sensor side of the jumper wire.
7. Connect black lead probe to ground.
8. Connect green lead probe to the ECM side of the jumper wire.
9.
Press menukey 3 (Lean) or 4 (Rich) to send out a Lean or Rich signal for 5
seconds.
PRIMARY DISPLAY
< 0.29999 V
0.3000 ~ 0.4499 V
0.4500 ~ 0.5999 V
0.6000 V
SECONDARY DISPLAY
X (Full Lean)
X (Lean)
X (Rich)
X (Full Rich)
Also during this test the menukey 3 (Lean) or menukey 4 (Rich) might be pressed
to send out a rich command or a lean command for 5 seconds, which will make the
“Lean” or “Rich” annunciator on menu screen flash depending upon which was
commended. During this time the primary display will show the signal level that is at
the O
2
Sensor to see that the condition is being compensated for. The green lead is
required to be connected between the “Signal” terminal and the O
2
connector on the
ECM side.
NOTE: Signal out and CC may not function properly on some Toyota O
2
Sensors.
