Code 0412

DTC 0412 (Left Bank, -B2) Front Heated Oxygen Sensor (Front HO2S) (High Voltage)







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 0V 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 airfoil ratio. The ideal air-fuel ratio occurs near the radical change from 1 V to 0V.




Consult Reference Value In Data Monitor Mode
Specification data are reference values.




ECM Terminals and Reference Value
ECM Terminals and Reference Value Specification data are reference values and are measured between each terminal and 32 (ECCS ground).







On Board Diagnosis Logic
To judge the malfunction, the diagnosis checks that the front heated oxygen sensor output is not inordinately high.

DTC Confirmation Procedure

NOTE: If "DTC Confirmation Procedure" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds
before conducting the next test.




With CONSULT
1. Turn ignition switch "ON".
2. Select "DATA MONITOR" mode with CONSULT and wait at least 5 seconds.

With GST
1. Turn ignition switch "ON" and wait at least 5 seconds.
2. Turn ignition switch "OFF" and wait at least 5 seconds
3. Turn ignition switch "ON" and wait at least 5 seconds.
4. Select "MODE 3" with GST.

No Tools
1. Turn ignition switch "ON" and wait at least 5 seconds.
2. Turn ignition switch "OFF" and wait at least 5 seconds
3. Perform "Diagnostic Test Mode II (Self-diagnostic results)" with ECM.

Steps 1 - 6:

Diagnostic Procedure




Wiring Diagram - Left Bank

Component Inspection










With CONSULT
1. Start engine and warm it up to normal operating temperature.
2. Select "MANU TRIG" and "HI SPEED" in "DATA MONITOR" mode with CONSULT and select "FR O2 SEN-B1 (-B2)" and "FR O2 MNTR-B1 (-B2)".
3. Hold engine speed at 2,000 rpm under no load during the following steps.
4. Touch "RECORD" on CONSULT screen.
5. Check the following.
- "FR O2 MNTR-B1 (-B2)" in "DATA MONITOR" mode changes from "RICH" to "LEAN" to "RICH" 5 times in 10 seconds.
5 times (cycles) are counted as shown left: R = "FR O2 MNTR-B1 (-B2)", "RICH" L = "FR O2 MNTR-B1 (-B2)", "LEAN"
- "FR O2 SEN-B1 (-B2)" voltage goes above 0.6V at least once.
- "FR O2 SEN-B1 (-B2)" voltage goes below 0.3V at least once.
- "FR O2 SEN-B1 (-B2)" voltage never exceeds 1 .0V.

CAUTION: Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.




Without CONSULT
1. Start engine and warm it up to normal operating temperature.
2. Set voltmeter probes between ECM terminal 50 (right bank sensor signal) or 51 (left bank sensor signal) and engine ground.
3. Check the following with engine speed held at 2,000 rpm constant under no load.
- MIL goes on more than 5 times within 10 seconds in Diagnostic Test Mode II (FRONT HEATED OXYGEN SENSOR MONITOR).
- The maximum voltage is over 0.6V at least one time.
- The minimum voltage is below 0.3V at least one time.
- The voltage never exceeds 1.0V.

CAUTION: Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.