DTC Description
DTC DETECTION 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 No. | CONSULT screen terms (Trouble diagnosis content) | DTC detecting con | |
| P0138 | HO2S2 (B1) (O2 sensor circuit high voltage bank 1 sensor 2) | A | An excessively high voltage from the sensor is sent to ECM |
| B | The minimum voltage from the sensor is not reached to the specified voltage. | ||
POSSIBLE CAUSE
DTC P0138 - A
DTC P0138 - B
FAIL-SAFE
Not applicable
DTC CONFIRMATION PROCEDURE
1.PRECONDITIONING
If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.
>> GO TO 2.
2.PERFORM DTC CONFIRMATION PROCEDURE FOR MALFUNCTION A
Is 1st trip DTC detected? YES >> Proceed to EC-244, "Diagnosis Procedure".
NO-1 >> With CONSULT: GO TO 3.
NO-2 >> Without CONSULT: GO TO 5.
3.PERFORM DTC CONFIRMATION PROCEDURE FOR MALFUNCTION B
NOTE: For better results, perform “DTC WORK SUPPORT” at a temperature of 0 to 30°C (32 to 86°F).
If not, warm up engine and go to next step when “COOLAN TEMP/S” indication reaches 70°C (158°F).
NOTE: It will take at most 10 minutes until “COMPLETED” is displayed.
Which is displayed on CONSULT
OK >> INSPECTION END
NG >> Proceed to EC-244, "Diagnosis Procedure".
CAN NOT BE DIAGNOSED>>GO TO 4.
4.PERFORM DTC CONFIRMATION PROCEDURE FOR MALFUNCTION B AGAIN
>> GO TO 3.
5.PERFORM COMPONENT FUNCTION CHECK-1
Without CONSULT

Is the inspection result normal? YES >> INSPECTION END
NO >> GO TO 6.
6.PERFORM COMPONENT FUNCTION CHECK-2
Check the voltage between ECM harness connector and ground as per the following condition.

Is the inspection result normal? YES >> INSPECTION END
NO >> GO TO 7.
7.PERFORM COMPONENT FUNCTION CHECK-3
Check the voltage between ECM harness connector and ground as per the following condition.

Is the inspection result normal? YES >> INSPECTION END
NO >> Proceed to EC-244, "Diagnosis Procedure".
Diagnosis Procedure
1.INSPECTION START
Confirm the detected malfunction (A or B). Refer to EC-242, "DTC Description".
Which malfunction is detected? A >>GO TO 2.
B >>GO TO 7.
2.CHECK HO2S2 CONNECTOR FOR WATER
Water should not exist.
Is the inspection result normal? YES >> GO TO 3.
NO >> Repair or replace error-detected parts.
3.CHECK HO2S2 GROUND CIRCUIT

Is the inspection result normal? YES >> GO TO 4.
NO >> Repair or replace error-detected parts.
4.CHECK HO2S2 INPUT SIGNAL CIRCUIT


Is the inspection result normal? YES >> GO TO 5.
NO >> Repair or replace error-detected parts.
5.CHECK HEATED OXYGEN SENSOR 2
Check the heated oxygen sensor 2. Refer to EC-247, "Component Inspection".
Is the inspection result normal? YES >> Check intermittent incident. Refer to GI-41, "Intermittent Incident".
NO >> GO TO 6.
6.REPLACE HEATED OXYGEN SENSOR 2
Replace heated oxygen sensor 2. Refer to EX-5, "Exploded View".
CAUTION:
>> INSPECTION END
7.CLEAR THE MIXTURE RATIO SELF-LEARNING VALUE
Is the 1st trip DTC P0172 detected? Is it difficult to start engine? YES >> Perform trouble diagnosis for DTC P0172. Refer to EC-265, "DTC Description".
NO >> GO TO 8.
8.CHECK HO2S2 GROUND CIRCUIT

Is the inspection result normal? YES >> GO TO 9.
NO >> Repair or replace error-detected parts.
9.CHECK HO2S2 INPUT SIGNAL CIRCUIT


Is the inspection result normal? YES >> GO TO 10.
NO >> Repair open circuit or short to ground or short to power in harness or connectors.
10.CHECK HEATED OXYGEN SENSOR 2
Check the heated oxygen sensor 2. Refer to EC-247, "Component Inspection".
Is the inspection result normal? YES >> Check intermittent incident. Refer to GI-41, "Intermittent Incident".
NO >> GO TO 11.
11.REPLACE HEATED OXYGEN SENSOR 2
Replace heated oxygen sensor 2. Refer to EX-5, "Exploded View".
CAUTION:
>> INSPECTION END
Component Inspection
1.INSPECTION START
Do you have CONSULT? Do you have CONSULT? YES >> GO TO 2.
NO >> GO TO 3.
2.CHECK HEATED OXYGEN SENSOR 2
With CONSULT

“HO2S2 (B1)” should be above 0.73 V at least once when the “FUEL INJECTION” is + 25%.
“HO2S2 (B1)” should be below 0.18 V at least once when the “FUEL INJECTION” is − 25%.
Is the inspection result normal? YES >> INSPECTION END
NO >> GO TO 6.
3.CHECK HEATED OXYGEN SENSOR 2-1
Without CONSULT

Is the inspection result normal? YES >> INSPECTION END
NO >> GO TO 4.
4.CHECK HEATED OXYGEN SENSOR 2-2
Check the voltage between ECM harness connector and ground as per the following condition.

Is the inspection result normal?
YES >> INSPECTION END
NO >> GO TO 5.
5.CHECK HEATED OXYGEN SENSOR 2-3
Check the voltage between ECM harness connector and ground as per the following condition.

Is the inspection result normal? YES >> INSPECTION END
NO >> GO TO 6.
6.REPLACE HEATED OXYGEN SENSOR 2
Replace heated oxygen sensor 2. Refer to EX-5, "Exploded View".
CAUTION:
>> INSPECTION END
P0137 HO2S2
P0139 HO2S2System description
DESCRIPTION
Engine Cooling System
Thermostat
Water outlet
Cylinder block (Thermostat housing)
Water inlet
Radiator
Water pump
Cylinder block
Cylinder head
Open
Closed
To electric throttle control actuator
To oil cooler
...
ECU diagnosis information
A/C AUTO AMP.
Reference Value
VALUES ON THE DIAGNOSIS TOOL
TERMINAL LAYOUT
PHYSICAL VALUES
DTC Inspection Priority Chart
If some DTCs are displayed at the same time, perform inspections one by one
based on the following priority
chart.
Priority
Det ...
CVT fluid cooler system
Cleaning
Whenever an automatic transaxle is repaired, overhauled, or replaced, the CVT
fluid cooler mounted in the
radiator must be inspected and cleaned.
Metal debris and friction material, if present, can be trapped or be deposited
in the CVT fluid cooler. This
debris can contaminate the ...