P0172

Wiring Diagram:

CIRCUIT DESCRIPTION
The oxygen sensor-1 is installed on the exhaust manifold (precatalyst) and the oxygen sensor-2 is installed on the exhaust pipe (post catalyst). Each sensor detect the concentration of oxygen in the exhaust gases.

ECM (PCM) detects the air-fuel ratio of the mixture supplied to the engine by monitoring the signal (output voltage) from sensor-1.The signal (output voltage) from sensor-2 is used to detect malfunction of the three way catalytic converter.

Each oxygen sensor heater promotes activation of the oxygen sensor.

Detecting Condition / 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.

1. Turn ignition switch OFF
2. Clear DTC with ignition switch ON.
3. Check vehicle and environmental condition for:
- Indication of fuel level meter in combination meter: 1/4 or more
- Altitude (barometric pressure): 2400 m, 8000 ft or less (560 mm Hg, 75 kPa or more)
- Ambient temp. : -10 °C, 14 °F or higher
- Intake air temp.: 70 °C, 158 °F or lower
4. Start engine and drive vehicle under usual driving condition for 5 min or longer and until engine is warmed up to normal operating temperature.
5. keep vehicle speed at 30 - 40 mph, 50 - 60 kph in 5th gear or "D" range for 5 min. or more.
6. Stop vehicle (do not turn ignition switch OFF).
7. Check pending DTC in "ON BOARD TEST" or "PENDING DTC" mode and DTC in "DTC" mode.

Step 1 - 7:

Step 8 - 11:

Fig. 1, 2, 3, 4, 5, 6, For Step 3, 4, 5, 6: