P0172

SYSTEM DIAGRAM/CIRCUIT DESCRIPTION




HEATED OXYGEN SENSOR-1 (HO2S-1)
The oxygen sensor is installed on the exhaust manifold (pre-catalyst) to detect the concentration of oxygen in the exhaust gases.

The oxygen sensor heater promotes activation of the oxygen sensor.




HEATED OXYGEN SENSOR-2 (HO2S-2)
The oxygen sensor is installed on the exhaust pipe (post-catalyst) to detect the concentration of oxygen in the exhaust gases just like HO2S-1.

ECM (PCM) judges deterioration of TWC (three way catalytic converter) by comparing waveforms of the output voltage from HO2S-1 and HO2S-2.

DTC Detecting Condition And Possible Cause:

DTC CONFIRMATION PROCEDURE

WARNING:
- When performing a road test, select a place where there is no traffic or possibility of a traffic accident and be very careful during testing to avoid occurrence of an accident.
- Road test should be carried out with 2 persons, a driver and a tester, on a level road.

NOTE: Check to make sure that following conditions are satisfied when using this "DTC CONFIRMATION PROCEDURE".
- Intake air temp. at start: -8 - 60 °C (18 - 140 °F)
- Engine coolant temp. at start: -8 - 95 °C (18 - 203 °F)
- Altitude (barometric pressure): 2400 m, 8000 ft or less (560 mmHg (75 kPa) or more)
- Intake air temp.: -8 °C (18 °F) or higher
- Engine coolant temp.: 110 °C (230 °F) or lower
- Fuel level indication on meter cluster: 1/4 or more

1. Connect scan tool to DLC with ignition switch OFF.
2. Turn ON ignition switch and clear DTC, pending DTC and freeze frame data by using scan tool and warm up engine completely.
3. Increase vehicle speed to 50 - 60 km/h (30 - 40 mph).
4. Keep driving above vehicle speed for 3 min. or more.
5. Stop vehicle and check pending DTC by using scan tool.

Step 1 - 4:

TROUBLESHOOTING