4-48 FI SYSTEM DIAGNOSIS
Step 2
1) Warm up the engine enough.
2) Insert the needle pointed probes to the HO2 sensor coupler.
3) Measure the HO2 sensor output voltage at the coupler
(between W/G and B/Br wires) when idling condition.
4) Also, measure the HO2 sensor output voltage while holding
the engine speed at 5 000 r/min.
% HO2 sensor output voltage at idle speed:
0.4 V and less (
+ W/G –
- B/Br)
HO2 sensor output voltage at 5 000 r/min:
0.6 V and more (
+ W/G –
- B/Br)
! 09900-25008: Multi circuit tester set
09900-25009: Needle pointed probe set
' Tester knob indication: Voltage (()
Is the voltage OK?
Step 3
1) Turn the ignition switch OFF.
2) Disconnect the HO2 sensor coupler.
3) Check the resistance between the terminals (White – White)
of the HO2 sensor.
% HO2 heater resistance:4 – 5 Ω (at 23 °C/73.4 °F)
(White – White)
NOTE:
* Temperature of the sensor affects resistance value largely.
* Make sure that the sensor heater is at correct temperature.
! 09900-25008: Multi circuit tester set
& Tester knob indication: Resistance (Ω)
Is the resistance OK?
YES Go to Step 3
NO Replace the HO2 sensor with a new one.
YES
• W/B, O/G, W/G or B/Br wire open or shorted to
ground, or poor
8,
9,
N or
X connection.
• If wire and connection are OK, intermittent trou-
ble or faulty ECM.
• Recheck each terminal and wire harness for
open circuit and poor connection.
NO Replace the HO2 sensor with a new one.
2
V
3
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