ENGINE (DIAGNOSTICS)(H4DO) > Diagnostic Procedure with Diagnostic Trouble Code (DTC)

DTC P1137 O2 SENSOR CIRCUIT (MID) (BANK 1 SENSOR 1)

DTC DETECTING CONDITION:

Immediately at fault recognition

CAUTION:

After repairing or replacing the defective part, perform the Clear Memory Mode and Inspection Mode .

WIRING DIAGRAM:

STEPCHECKYESNO

1.CHECK FOR ANY OTHER DTC ON DISPLAY.

Is any other DTC displayed?

Check DTC using “List of Diagnostic Trouble Code (DTC)”.

2.CHECK FRONT OXYGEN (A/F) SENSOR DATA.

1) Start the engine.

2) While observing the Subaru Select Monitor or general scan tool screen, warm up the engine until engine coolant temperature is above 75°C (167°F).

When the engine is already warmed up, keep the engine idling for more than one minute.

3) Read the data of front oxygen (A/F) sensor signal using Subaru Select Monitor or general scan tool.

NOTE:

• Subaru Select Monitor

For detailed operation procedures, refer to “READ CURRENT DATA FOR ENGINE”.

• General scan tool

For detailed operation procedures, refer to the general scan tool operation manual.

Is the voltage 2 — 2.3 V?

3.CHECK FRONT OXYGEN (A/F) SENSOR DATA.

Race the engine at speeds from idling to 3,000 rpm for a total of 5 cycles.

NOTE:

• Normally, the air fuel ratio is rich at racing.

• To increase engine speed to 3,000 rpm, slowly depress accelerator pedal for approximately 5 seconds, and quickly release accelerator pedal to decrease engine speed.

Is the voltage less than 2.15 V?

4.CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR.

1) Turn the ignition switch to OFF.

2) Disconnect the connectors from the ECM and front oxygen (A/F) sensor.

3) Measure the resistance of harness between ECM and front oxygen (A/F) sensor.

Connector & terminal

(B137) No. 23 — (E23) No. 3:

(B137) No. 14 — (E23) No. 1:

Is the resistance less than 1 Ω?

Repair the harness and connector.

NOTE:

In this case, repair the following item:

• Open circuit in harness between ECM and front oxygen (A/F) sensor

• Poor contact of coupling connector

5.CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR.

Measure the resistance between ECM and chassis ground.

Connector & terminal

(B137) No. 23 — Chassis ground:

(B137) No. 14 — Chassis ground:

Is the resistance 1 MΩ or more?

Repair the ground short circuit of harness between ECM and front oxygen (A/F) sensor.

6.CHECK EXHAUST SYSTEM.

Check exhaust system parts.

NOTE:

Check the following items.

• Loose part and improper installation of exhaust system

• Damage (crack, hole etc.) of parts

• Looseness of front oxygen (A/F) sensor

• 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 front oxygen (A/F) sensor.