P0154

Component Description
The front heated oxygen sensor is placed into the front tube. It detects the amount of oxygen in the exhaust gas compared to the outside air. The front heated oxygen sensor has a closed-end tube made of ceramic zirconia.The zirconia generates voltage from approximately 1 V in richer conditions to 0 V in leaner conditions. The front heated oxygen sensor signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1 V to 0 V.

CONSULT-II Reference Value in Data Monitor Mode
Specification data are reference values.

On Board Diagnosis Logic
To judge the malfunction, the diagnosis checks that the front heated oxygen sensor output is not inordinately high. Malfunction is detected when an excessively high voltage from the sensor is sent to ECM.

Possible Cause
- Harness or connectors
(The sensor circuit is open or shorted. )
- Front heated oxygen sensor

DTC Confirmation Procedure

NOTE: If "DTC Confirmation Procedure" has been previously conducted, always turn ignition switch "OFF" and wait at least 10 seconds before conducting the next test.

WITH CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch "OFF" and wait at least 10 seconds.
3. Turn ignition switch "ON".
4. Select "DATA MONITOR" mode with CONSULT-II.
5. Restart engine and let it idle for 25 seconds.
6. If 1st trip DTC is detected, go to "Diagnostic Procedure" below.

WITH GST
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch "OFF" and wait at least 10 seconds.
3. Restart engine and let it idle for 25 seconds.
4. Turn ignition switch "OFF" and wait at least 10 seconds.
5. Restart engine and let it idle for 25 seconds.
6. Select "MODE 3" with GST.
7. If DTC is detected, go to "Diagnostic Procedure" below.
- When using GST, "DTC Confirmation Procedure" should be performed twice as much as when using CONSULT-II because GST cannot display MODE 7 (1st trip DTC) concerning this diagnosis. Therefore, using CONSULT-II is recommended.

Wiring Diagram