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

WARNING: This page is about a different car, the 2006 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

DTC DETECTING CONDITION:

Two consecutive driving cycles with fault
GENERAL DESCRIPTION <Ref. to DTC P0140 O2 SENSOR CIRCUIT NO ACTIVITY DETECTED (BANK 1 SENSOR 2) , Diagnostic Trouble Code (DTC) Detecting Criteria. >

CAUTION: After repairing or replacing the defective part, carry out the Clear Memory Mode <Ref. to OPERATION , CLEAR MEMORY MODE. > and Inspection Mode <Ref. to PROCEDURE , INSPECTION MODE. >

WIRING DIAGRAM:

Fig 1: Identifying O2 Sensor Circuit No Activity Detected - Wiring Diagram (Bank1 Sensor2)

Courtesy of SUBARU OF AMERICA, INC.

TROUBLESHOOTING CHART

Step	Check	Yes	No
1 CHECK ANY OTHER DTC ON DISPLAY.	Is any other DTC displayed?	Check DTC using "List of Diagnostic Trouble Code (DTC)". <Ref. to LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . > NOTE: In this case, it is not necessary to inspect DTC P0137.	Go to step 2.
2 CHECK REAR OXYGEN SENSOR DATA. Warm-up the engine until engine coolant temperature is above 70°C (158°F), and keep the engine rpm at 5,000 rpm. Read the data of rear oxygen 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 ". <Ref. to SUBARU SELECT MONITOR . > General scan tool For detailed operation procedure, refer to the general scan tool operation manual.	Is the voltage more than 490 mV?	Go to step 6.	Go to step 3.
3 CHECK REAR OXYGEN SENSOR DATA. Warm-up the engine until engine coolant temperature is above 70°C (158°F), and keep the engine rpm at 5,000 rpm. Read the data of rear oxygen 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 ". <Ref. to SUBARU SELECT MONITOR . > General scan tool For detailed operation procedure, refer to the general scan tool operation manual.	Is the voltage less than 250 mV?	Go to step 6.	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 (B135) No. 4 - (B18) No. 3: (8135) No. 30 - (B18) No. 4:	Is the resistance more than 3 Ω?	Repair the open circuit of harness between ECM and rear oxygen sensor connector.	Go to step 5.
5 CHECK HARNESS BETWEEN REAR OXYGEN SENSOR AND ECM CONNECTOR. Turn the ignition switch to OFF. Disconnect the connector from the rear oxygen sensor. Turn the ignition switch to ON. Measure the resistance between the rear oxygen sensor harness connector and chassis ground. Connector & terminal (B18) 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 of harness between rear oxygen sensor and ECM connector Poor contact of the rear oxygen sensor connector Poor contact in ECM connector
6 CHECK EXHAUST SYSTEM. Check exhaust system parts. NOTE: Check the following item. Exhaust system part looseness and incomplete attachment Damage (crack, hole etc.) of parts Looseness and improper attachment of parts 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 . >