DTC P0140: O2 Sensor Circuit No Activity Detected (Bank1 Sensor2): Wiring Diagram

Engine electrical system non-turbo model (without push button start) < Ref. to NON-TURBO MODEL (WITHOUT PUSH BUTTON START) , WIRING DIAGRAM, Engine Electrical System. >
Engine electrical system non-turbo model (with push button start) < Ref. to NON-TURBO MODEL (WITH PUSH BUTTON START) , WIRING DIAGRAM, Engine Electrical System. >

Fig 1: HO2S Heater Control Circuit High (Bank 1 Sensor 2) - Wiring Diagram
Courtesy of SUBARU OF AMERICA, INC.

DTC PROCEDURE

Step	Check	Yes	No
1 CHECK REAR OXYGEN SENSOR DATA . Warm up the engine until engine coolant temperature is higher than 75°C (167°F), and keep the engine speed at 3, 000 rpm. (2 minutes maximum) Read the value of «Rear O2 Sensor» 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". < Ref. to SUBARU SELECT MONITOR . > General scan tool For detailed operation procedures, refer to the general scan tool operation manual.	Is the value of «Rear O2 Sensor » 0.490 V or more?	Go to step 6 .	Go to step 2 .
2 CHECK REAR OXYGEN SENSOR DATA . 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. Read the value of «Rear O2 Sensor» 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". < Ref. to SUBARU SELECT MONITOR . > General scan tool For detailed operation procedures, refer to the general scan tool operation manual.	Is the value of «Rear O2 Sensor » 0.250 V or less?	Go to step 6 .	Go to step 3 .
3 CHECK REAR OXYGEN SENSOR CONNECTOR AND COUPLING CONNECTOR .	Has water entered the connector?	Completely remove any water inside.	Go to step 4 .
4 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR . Turn the ignition switch to OFF. Disconnect the connector from ECM and rear oxygen sensor. Measure the resistance of harness between ECM and rear oxygen sensor connector. Connector & terminal (B136) No. 21 - (E25) No. 3: (B135) No. 30 - (E25) No. 4:	Is the resistance less than 1 Ω?	Go to step 5 .	Repair the harness and connector. NOTE: In this case, repair the following item: Open circuit in harness between ECM and rear oxygen sensor connector Poor contact of coupling connector
5 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR . Connect the connector to ECM. Turn the ignition switch to ON. Measure the voltage between rear oxygen sensor connector and chassis ground. Connector & terminal (E25) No. 3 (+) - Chassis ground (-):	Is the voltage 0.2 - 0.5 V?	Replace the rear oxygen sensor. < Ref. to REAR OXYGEN SENSOR . >	Repair the harness and connector. NOTE: In this case, repair the following item: Open circuit in harness between ECM and rear oxygen sensor connector Poor contact of coupling connector Poor contact of ECM connector
6 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. < Ref. to REAR OXYGEN SENSOR . >