DTC P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)

DTC DETECTING CONDITION:

Two consecutive driving cycles with fault
GENERAL DESCRIPTION < Ref. to DTC P0139 O2 SENSOR CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 2) , Diagnostic Trouble Code (DTC) Detecting Criteria. >

CAUTION: After repair or replacement of faulty parts, conduct Clear Memory Mode < Ref. to , OPERATION , Clear Memory Mode.> and Inspection Mode < Ref. to , PROCEDURE , Inspection Mode.>.

WIRING DIAGRAM:

Fig 1: Wiring Diagram - DTC P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE (DTC P0139)

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 P0139.	Go to step 2.
2 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 (B137) No. 25 - (T6) No. 3:	Is the resistance less than 1 ?	Go to step 3.	Repair harness and connector. NOTE: In this case, repair the following: Open circuit in harness between rear oxygen sensor and ECM connector
3 CHECK HARNESS BETWEEN REAR OXYGEN SENSOR AND ECM CONNECTOR. Measure the resistance between rear oxygen sensor harness connector and chassis ground. Connector & terminal (T6) No. 3 - Chassis ground:	Is the resistance more than 1 M?	Go to step 4.	Repair short circuit to ground in harness between rear oxygen sensor and ECM connector.
4 CHECK REAR OXYGEN SENSOR DATA. Measure the resistance between connector terminals of rear oxygen sensor. Terminals No. 3 - No. 4:	Is the resistance less than 1 ?	Replace the rear oxygen sensor. < Ref. to REAR OXYGEN SENSOR . >	Repair connector. Poor contact in rear oxygen sensor connector.