P0139

DTC P0139 HO2S2




Component Description
The heated oxygen sensor 2, after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank.

Even if switching characteristics of the heated oxygen sensor 1 are shifted, the air-fuel ratio is controlled to stoichiometric, by the signal from the heated oxygen sensor 2.

This sensor is made of ceramic zirconia. The zirconia generates voltage from approximately 1 V in richer conditions to 0 V in leaner conditions.

Undernormal conditions the heated oxygen sensor 2 is not used for engine control operation.

CONSULT-II Reference Value In Data Monitor Mode:

On Board Diagnosis Logic
The heated oxygen sensor 2 has a much longer switching time between rich and lean than the heated oxygen sensor 1. The oxygen storage capacity before the three way catalyst (manifold) causes the longer switching time. To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the switching response of the sensor's voltage is faster than specified during the various driving condition such as fuel-cut.

DTC Confirmation Procedure

NOTE: If "DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE" has been previously conducted, always turn ignition switch OFF and wait at least 5 seconds before conducting the next test.

TESTING CONDITION:
Open engine hood before conducting following procedure

WITH CONSULT-II
1. Start engine and warm it up to the normal operating temperature.
2. Turn ignition switch "OFF" and wait at least 10 seconds.
3. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least one minute under no load.
4. Let engine idle for one minutes.
5. Select "HO2S2 (B1) P0139" or "HO2S2 (B2) P0159" of "HO2S2" in "DTC WORK SUPPORT" mode with CONSULT-II and follow the instruction of CONSULT-II.




6. Start engine and following the instruction of CONSULT-II.

7. Make sure that "OK" is displayed after touching "SELF-DIAG RESULTS".
If "NG" is displayed, refer to "Diagnostic Procedure" below.
If "CAN NOT BE DIAGNOSED" is displayed, perform the following.
a. Turn ignition switch "OFF" and leave the vehicle in a cool place (soak the vehicle).
b. Turn ignition switch "ON" and select "COOLANTEMP/S" in "DATA MONITOR" mode with CONSULT-II.
c. Start engine and warm it up while monitoring "COOLANTEMP/S" indication on CONSULT-II.
d. When "COOLANTEMP/S" indication reaches to 70 °C (158 °F), go to step 3.

Overall Function Check
Use this procedure to check the overall function of the heated oxygen sensor 2 circuit. During this check, a DTC might not be confirmed.

CAUTION: Always drive vehicle at a safe speed.

WITH GST
1. Start engine and warm it up to the normal operating temperature.
2. Turn ignition switch "OFF" and wait at least 10 seconds.
3. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least one minute under no load.
4. Let engine idle for one minute.




5. Set voltmeter probes between ECM terminal 56 [HO2S2(B1) signal] or 57 [HO2S2(B2) signal] and ground.

6. Check the voltage when revving up to 4,000 rpm under no load at least 10 times.
(Depress and release accelerator pedal as soon as possible.)
The voltage should change at more than 0.06 V for 1 second during this procedure.
If the voltage can be confirmed in step 6, step 7 is not necessary.

7. Keep vehicle at idling for 10 minutes, then check the voltage. Or check the voltage when coasting from 80 km/h (50 MPH) in "D" position with "OD" OFF (A/T), 3rd gear position (M/T).
The voltage should change at more than 0.06 V for 1 second during this procedure.

8. If NG, go to "Diagnostic Procedure" below.

EC-O2S2B1-01:

EC-O2S2B2-01:

Wiring Diagram

Diagnostic Procedure

Diagnostic Procedure Step 1:

Diagnostic Procedure Step 2 - 4:

Diagnostic Procedure Step 5:

Diagnostic Procedure Step 6:

Diagnostic Procedure Step 7 - 8: