Identification

This article was updated by bulletin number: 11-92-08

Date: 01/05/09

APPLICABILITY:
1999MY and later Forester
1999MY and later Impreza
2000MY and later Legacy
2006MY and later Tribeca

SUBJECT:
Air/Fuel Ratio Sensor and Oxygen Sensor

INTRODUCTION

For information purposes only.

REPAIR/SERVICE INFORMATION

When performing diagnostics or reading Diagnostic Trouble Codes (DTC) for Air Fuel Ratio (A/F) sensors and Oxygen (O2) sensors use the following information to identify, locate and repair the appropriate sensor and sensor circuits:

(1) Rarely will multiple sensors fail at the same time.

(2) On vehicles with only one O2 sensor, the designation for that O2 sensor will be bank 1.

(3) On vehicles with only one A/F sensor, the designation for that A/F sensor will be bank 1.

(4) Any reference to sensor 1 is an A/F sensor.

(5) Any reference to sensor 2 is an O2 sensor.

(6) Early PZEV vehicles used an additional O2 sensor behind the rear catalyst and is designated sensor 3.

(7) On vehicles with A/F and O2 sensors on the right (Passenger Side) and left (Driver side) of the vehicle, Bank 1 is the right side (Passenger Side) and Bank 2 is the left side (Driver side).

Example: DTC P0030 HO2S HEATER CONTROL CIRCUIT (Bank 1 Sensor 1). This DTC is referring to the A/F sensor and since it is on a 2007 Forester there is only one A/F sensor and one O2 sensor.





Example (as illustrated): DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW (Bank 1 Sensor 2). This DTC is referring to the O2 sensor on the right side exhaust (or the O2 sensor of a vehicle with only one O2 sensor).











Refer to the illustrations above for more details on locating the appropriate sensors.





The list shown above is of A/F Sensor related DTCs. (This list is for example only. Refer to the applicable service manual for a complete list of DTCs.)

Note:
When the DTCs for A/F sensor are stored in memory, do not replace the oxygen sensor.





The list above is of O2 Sensor related DTCs. (This list is for example only. Refer to the applicable service manual for a complete list of DTCs.)

Note:
When the DTCs for O2 sensor are stored in memory, do not replace the A/F sensor.











P Code List (Partial list)