Subaru Legacy BN/BS (2015-2019) Service Manual: Dtc p0138 o2 sensor circuit high voltage bank 1 sensor 2

Subaru Legacy BN/BS (2015-2019) Service Manual / Engine (diagnostics)(h4do) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc p0138 o2 sensor circuit high voltage bank 1 sensor 2

DTC DETECTING CONDITION:

Detected when two consecutive driving cycles with fault occur.

CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Mode Clear Memory Mode > OPERATION, and Inspection Mode Inspection Mode > PROCEDURE.

WIRING DIAGRAM:

• Engine Electrical System ENGINE TYPE FB (WITHOUT PUSH BUTTON START) Engine Electrical System > WIRING DIAGRAM

• Engine Electrical System ENGINE TYPE FB (WITH PUSH BUTTON START) Engine Electrical System > WIRING DIAGRAM

STEP	CHECK	YES	NO
1.CHECK REAR OXYGEN SENSOR DATA. 1) Warm up the engine until engine coolant temperature is higher than 75°C (167°F), and rapidly reduce the engine speed from 3,000 rpm. 2) Read the value of «Oxygen sensor #12» using the Subaru Select Monitor or a general scan tool. NOTE: • Subaru Select Monitor For detailed operation procedures, refer to “Read Current Data For Engine”. Subaru Select Monitor • General scan tool For detailed operation procedures, refer to the general scan tool operation manual.	Is the value of «Oxygen sensor #12» 0.250 V or less-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0138 O2 SENSOR CIRCUIT HIGH VOLTAGE BANK 1 SENSOR 2	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0138 O2 SENSOR CIRCUIT HIGH VOLTAGE BANK 1 SENSOR 2
2.CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR.	Has water entered the connector-	Completely remove any water inside.	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0138 O2 SENSOR CIRCUIT HIGH VOLTAGE BANK 1 SENSOR 2
3.CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. 1) Turn the ignition switch to OFF. 2) Disconnect the connector from ECM and rear oxygen sensor. 3) Measure the resistance of harness between ECM connector and rear oxygen sensor connector. Connector & terminal (E158) No. 57 — (E25) No. 3: (E158) No. 56 — (E25) No. 4:	Is the resistance less than 1 --	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0138 O2 SENSOR CIRCUIT HIGH VOLTAGE BANK 1 SENSOR 2	Repair the harness and connector. NOTE: In this case, repair the following item: • Open circuit in harness between ECM connector and rear oxygen sensor connector
4.CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR. 1) Connect the connector to ECM. 2) Turn the ignition switch to ON. 3) Measure the voltage between rear oxygen sensor connector and chassis ground. Connector & terminal (E25) No. 3 (+) — Chassis ground (−):	Is the voltage 1.78 V or less-	Replace the rear oxygen sensor. Rear Oxygen Sensor	Replace the ECM.
5.CHECK EXHAUST SYSTEM. Check exhaust system parts. NOTE: Check the following items. • Looseness and improper fitting of exhaust system parts • Damage (crack, hole etc.) of parts • Loose part and improper installation between front oxygen (A/F) sensor and rear oxygen sensor	Is there any fault in exhaust system-	Repair or replace faulty parts.	Replace the rear oxygen sensor. Rear Oxygen Sensor

1. OUTLINE OF DIAGNOSIS

Detect for NG of the rear oxygen sensor continuity.

Judge as NG if the rear oxygen sensor voltage is not within the possible range.

2. COMPONENT DESCRIPTION

(A)	Electromotive force	(B)	Air fuel ratio	(C)	Rich
(D)	Lean	(E)	Theoretical air fuel ratio	(F)	Comparative voltage

(1)	Atmosphere	(2)	Exhaust gas	(3)	Electromotive force

3. EXECUTION CONDITION

Secondary Parameters	Execution condition
Battery voltage	≥ 10.9 V

4. GENERAL DRIVING CYCLE

Always perform the diagnosis continuously.

5. DIAGNOSTIC METHOD

If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.

Judgment Value

Malfunction Criteria	Threshold Value
Judgment 1: Short to battery
Secondary oxygen sensor offset signal	≥ 1.68 V
Judgment 2: Short to battery
Secondary oxygen sensor signal	≥ 2.73 V
Judgment 3: Out of range
Secondary oxygen sensor output voltage	≥ 1.2 V

Time Needed for Diagnosis: 1000 ms

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

Dtc p013a o2 sensor slow response - rich to lean bank 1 sensor 2

DTC DETECTING CONDITION:Detected when two consecutive driving cycles with fault occur.CAUTION:After servicing or replacing faulty parts, perform Clear Memory Mode Clear Memory Mode > OPERATION, and I ...

Dtc p0137 o2 sensor circuit low voltage bank 1 sensor 2

Other materials:

Disassembly
1. RADIATOR MAIN FAN AND MAIN FAN MOTOR1. Disengage the clip securing the connector of the radiator main fan motor to the radiator fan shroud, and remove the radiator main fan motor harness from the clips (A).2. Remove the radiator main fan from the radiator main fan motor.3. Remove the radiator mai ...