P0138

P0138, P0158 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 air fuel ratio (A/F) 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.

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

On Board Diagnosis Logic

The heated oxygen sensor 2 has a much longer switching time between rich and lean than the air fuel ratio (A/F) sensor 1. The oxygen storage capacity of the three way catalyst (manifold) causes the longer switching time.

Malfunction A

To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the voltage is unusually high during the various driving condition such as fuel-cut.





Malfunction B

To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the minimum voltage of sensor is sufficiently low during the various driving condition such as fuel-cut.











DTC Confirmation Procedure

Perform PROCEDURE FOR MALFUNCTION A first.

If DTC cannot be confirmed, perform PROCEDURE FOR MALFUNCTION B.

NOTE:

If DTC Confirmation Procedure has been previously conducted, always perform the following before conducting the next step.

1) Turn ignition switch OFF and wait at least 10 seconds.
2) Turn ignition switch ON.
3) Turn ignition switch OFF and wait at least 10 seconds.

Procedure for Malfunction A

With SDT

1) Turn ignition switch ON and select "Data list" mode with SDT.
2) Start engine and warm it up to the normal operating temperature.
3) Turn ignition switch OFF and wait at least 10 seconds.
4) Turn ignition switch ON.
5) Turn ignition switch OFF and wait at least 10 seconds.
6) Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
7) Let engine idle for 2 minutes.
8) Check 1st trip DTC.
9) If 1st trip DTC is detected, go to "Diagnosis Procedure".

With GST

Follow the procedure "WITH SDT" above.

Procedure for Malfunction B

With SDT

TESTING CONDITION:

For better results, perform "DTC work support" at a temperature of 0 to 30 °C (32 to 86 °F).
1) Turn ignition switch ON and select "Data list" mode with SDT.
2) Start engine and warm it up to the normal operating temperature.
3) Turn ignition switch OFF and wait at least 10 seconds.
4) Turn ignition switch ON.
5) Turn ignition switch OFF and wait at least 10 seconds.
6) Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
7) Let engine idle for 1 minute.
8) Check that "COOLAN TEMP/S" indicates more than 70 °C (158 °F).

If not, warm up engine and go to next step when "COOLAN TEMP/S" indication reaches 70 °C (158 °F).
9) Open engine hood.
10) Select "HO2S2 (B1) P1146" (for DTC P138) or "HO2S2 (B2) P1166" (for DTC P0158) of "HO2S2" in "DTC work support" mode with SDT.
11) Follow the instruction of SDT.

NOTE:
It will take at most 10 minutes until "COMPLETED" is displayed.

12) Check that "OK" is displayed after touching "DTC check".

If "NG" is displayed, refer to "Diagnosis Procedure".

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) Return to step 1.

Overall Function Check

Procedure for Malfunction B

Use this procedure to check the overall function of the heated oxygen sensor 2 circuit. During this check, a 1st trip DTC might not be confirmed.

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) Turn ignition switch ON.
4) Turn ignition switch OFF and wait at least 10 seconds.
5) Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
6) Let engine idle for 1 minute.
7) Set voltmeter probes between ECM terminal 74 [HO2S2 (B1) signal] or 55 [HO2S2 (B2) signal] and ground.
8) 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 be below 0.18 V at least once during this procedure.

If the voltage can be confirmed in step 6, step 7 is not necessary.
9) 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), 5th gear position (M/T).

The voltage should be below 0.18 V at least once during this procedure.
10) If NG, go to "Diagnosis Procedure".

Diagnosis Procedure

Procedure for Malfunction A

1. CHECK GROUND CONNECTIONS

1 Turn ignition switch OFF.
2 Loosen and retighten three ground screws on the body. Refer to [Power Supply and Ground Circuit Check] Power Supply and Ground Circuit Check.






OK or NG
OK
GO TO 2.
NG
Repair or replace ground connections.

2. CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT

1 Disconnect heated oxygen sensor 2 harness connector.





2 Disconnect ECM harness connector.
3 Check harness continuity between HO2S2 terminal 4 and ECM terminal 78.
Refer to Wiring Diagram.






4 Also check harness for short to ground and short to power.

OK or NG
OK
GO TO 3.
NG
Repair open circuit or short to ground or short to power in harness or connectors.

3. CHECK HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1 Check harness continuity between ECM terminal and HO2S2 terminal as follows.
Refer to Wiring Diagram.










2 Check harness continuity between the following terminals and ground.
Refer to Wiring Diagram.










3 Also check harness for short to power.

OK or NG
OK
GO TO 4.
NG
Repair open circuit or short to ground or short to power in harness or connectors.

4. CHECK HO2S2 CONNECTOR FOR WATER

Check connectors for water.






OK or NG
OK
GO TO 5.
NG
Repair or replace harness or connectors.

5. CHECK HEATED OXYGEN SENSOR 2

Refer to "Component Inspection".

OK or NG
OK
GO TO 6.
NG
Replace malfunctioning heated oxygen sensor 2. Refer to [Exhaust System: Exploded View] Exploded View.

6. CHECK INTERMITTENT INCIDENT

Refer to [Service Information for Electrical Incident: Intermittent Incident] Service Information for Electrical Incident: Intermittent Incident.


INSPECTION END

Procedure for Malfunction B

1. CHECK GROUND CONNECTIONS

1 Turn ignition switch OFF.
2 Loosen and retighten three ground screws on the body. Refer to [Power Supply and Ground Circuit Check] Power Supply and Ground Circuit Check.






OK or NG
OK
GO TO 2.
NG
Repair or replace ground connections.

2. CLEAR THE SELF-LEARNING DATA

With SDT
1 Start engine and warm it up to normal operating temperature.
2 Select "SELF-LEARNING CONT" in "Utility" mode with SDT.
3 Clear the self-learning control coefficient by touching "CLEAR".
4 Run engine for at least 10 minutes at idle speed.
Is the 1st trip DTC P0172 or P0175 detected?
Is it difficult to start engine?
Without SDT
1 Start engine and warm it up to normal operating temperature.
2 Turn ignition switch OFF.
3 Disconnect mass air flow sensor harness connector, and restart and run engine for at least 5 seconds at idle speed.





4 Stop engine and reconnect mass air flow sensor harness connector.
5 Check DTC P0102 is displayed.
6 Erase the DTC memory. Refer to [On Board Diagnosis Function] On Board Diagnosis Function (Without SDT) or [SDT Function] SDT Function (With SDT).
7 Check DTC P0000 is displayed.
8 Run engine for at least 10 minutes at idle speed.
Is the 1st trip DTC P0172 or P0175 detected?
Is it difficult to start engine?

Yes or No
Yes
Perform trouble diagnosis for DTC P0172, P0175. Refer to [P0172, P0175 Fuel Injection System Function] P0172.
No
GO TO 3.

3. CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT

1 Turn ignition switch OFF.
2 Disconnect heated oxygen sensor 2 harness connector.





3 Disconnect ECM harness connector.
4 Check harness continuity between HO2S2 terminal 4 and ECM terminal 78.
Refer to Wiring Diagram.






5 Also check harness for short to ground and short to power.

OK or NG
OK
GO TO 4.
NG
Repair open circuit or short to ground or short to power in harness or connectors.

4. CHECK HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1 Check harness continuity between ECM terminal and HO2S2 terminal as follows.
Refer to Wiring Diagram.










2 Check harness continuity between the following terminals and ground.
Refer to Wiring Diagram.










3 Also check harness for short to power.

OK or NG
OK
GO TO 5.
NG
Repair open circuit or short to ground or short to power in harness or connectors.

5. CHECK HEATED OXYGEN SENSOR 2

Refer to "Component Inspection".

OK or NG
OK
GO TO 6.
NG
Replace malfunctioning heated oxygen sensor 2. Refer to [Exhaust System: Exploded View] Exploded View.

6. CHECK INTERMITTENT INCIDENT

Refer to [Service Information for Electrical Incident: Intermittent Incident] Service Information for Electrical Incident: Intermittent Incident.


INSPECTION END

Component Inspection

Heated Oxygen Sensor 2

With SDT

1) Turn ignition switch ON and select "Data list" mode with SDT.
2) Start engine and warm it up to the normal operating temperature.
3) Turn ignition switch OFF and wait at least 10 seconds.
4) Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
5) Let engine idle for 1 minute.
6) Select "FUEL INJECTION" in "Active test" mode, and select "HO2S2 (B1)/(B2)" as the monitor item with SDT.
7) Check "HO2S2 (B1)/(B2)" at idle speed when adjusting "FUEL INJECTION" to ±25%.





"HO2S2 (B1)/(B2)" should be above 0.68 V at least once when the "FUEL INJECTION" is +25%.

"HO2S2 (B1)/(B2)" should be below 0.18 V at least once when the "FUEL INJECTION" is -25%.

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.
- Before installing new oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.

Without SDT

8) Start engine and warm it up to the normal operating temperature.
9) Turn ignition switch OFF and wait at least 10 seconds.
10) Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
11) Let engine idle for 1 minute.
12) Set voltmeter probes between ECM terminal 74 [HO2S2 (B1) signal] or 55 [HO2S2 (B2) signal] and ground.
13) 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 be above 0.68 V at least once during this procedure.

If the voltage is above 0.68 V at step 6, step 7 is not necessary.
14) Keep vehicle at idling for 10 minutes, then check voltage. Or check the voltage when coasting from 80 km/h (50 MPH) in D position with "OD" OFF (A/T), 5th gear position (M/T).

The voltage should be below 0.18 V at least once during this procedure.
15) If NG, replace heated oxygen sensor 2.

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.
- Before installing new oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.