DTC P0140 - O2 Sensor Circuit Range/Performance (Bank 1 Sensor 2) -

DTC DETECTING CONDITION:
- Two consecutive driving cycles with malfunction
- GENERAL DESCRIPTION < Ref. to DTC P0140 - O2 SENSOR CIRCUIT RANGE/PERFORMANCE (BANK 1 SENSOR 2) - , Diagnostic Trouble Code (DTC) Detecting Criteria. >
CAUTION: After repair or replacement of malfunctioning parts, conduct Clear Memory Mode < Ref. to CLEAR MEMORY MODE >and Inspection Mode < Ref. to INSPECTION MODE . >
WIRING DIAGRAM:

Fig 1: O2 Sensor Circuit Range/Performance Wiring Diagram
Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK ANY OTHER DTC ON DISPLAY.	Is any other DTC displayed?	Using the List of Diagnostic Trouble Code (DTC), check the appropriate DTC. < Ref. to LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . > NOTE: In this case, it is not necessary to inspect P0140. NOTE: Go to step 2.	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 speed 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 procedure, refer to the "READ CURRENT DATA FOR ENGINE". < Ref. to SUBARU SELECT MONITOR . > General scan tool For detailed operation procedures, refer to the General Scan Tool Instruction Manual.	Is the measured value is 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 speed 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 procedure, refer to the "READ CURRENT DATA FOR ENGINE". < Ref. to SUBARU SELECT MONITOR . > General scan tool For detailed operation procedures, refer to the General Scan Tool Instruction Manual.	Is the measured value is 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 connectors from ECM and rear oxygen sensor. Measure the resistance of harness between ECM and rear oxygen sensor connector. Connector & terminal (B135) No. 19 - (T6) No. 3: (B135) No. 14 - (T6) No. 4:	Is the measured value is less than 3 Ω?	Repair the open circuit in 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 rear oxygen sensor. Turn the ignition switch to ON. Measure the voltage of harness between rear oxygen sensor connector and chassis ground. Connector & terminal (T6) No. 4 - Chassis ground:	Is the measured value within 0.2 to 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: Open circuit in harness between rear oxygen sensor and ECM connector. Poor contact in rear oxygen sensor connector Poor contact in ECM connector
6 CHECK EXHAUST SYSTEM. Check exhaust system parts. NOTE: Check the following items. Looseness of and ill-fitting exhaust system parts Damage (crack, hole, etc.) Looseness of and ill-fitting parts between front oxygen (A/F) sensor and rear oxygen sensor	Is there any malfunction in exhaust system?	Repair or replace the malfunctioning parts.	Replace the rear oxygen sensor. < Ref. to REAR OXYGEN SENSOR . >