DTC P0159 O2 Sensor Circuit Slow Response (Bank 2 Sensor 2): Wiring Diagram

Fig 1: HO2S Heater Control Circuit - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 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. 15 - (E25) No. 3:	Is the resistance less than 1 Ω?	Go to step 2.	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
2 CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR.  Measure the resistance between rear oxygen sensor connector and chassis ground. Connector & terminal  (B25) No. 3 - Chassis ground:	Is the resistance 1 MΩ or more?	Go to step 3.	Repair the ground short circuit of harness between ECM and rear oxygen sensor connector.
3 CHECK REAR OXYGEN SENSOR.  Measure the resistance between rear oxygen sensor terminals. Terminals  No. 3 - No. 4	Is the resistance less than 1 Ω?	Replace the rear oxygen sensor. Ref. to REAR OXYGEN SENSOR .	If DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again. NOTE: In this case, temporary poor contact of connector may be the cause.