Subaru Legacy Service Manual: Dtc p2271 o2 sensor signal biased/stuck rich bank 1 sensor 2
Subaru Legacy Service Manual / Engine (diagnostics)(h4do) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc p2271 o2 sensor signal biased/stuck rich bank 1 sensor 2






DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode Clear Memory Mode > OPERATION, and Inspection Mode Inspection Mode > PROCEDURE.
WIRING DIAGRAM:
• Engine Electrical System ENGINE TYPE FB (WITHOUT PUSH BUTTON START) Engine Electrical System > WIRING DIAGRAM
• Engine Electrical System ENGINE TYPE FB (WITH PUSH BUTTON START) Engine Electrical System > WIRING DIAGRAM

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STEPCHECKYESNO
1.CHECK REAR OXYGEN SENSOR CONNECTOR.Has water entered the connector-Completely remove any water inside.Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P2271 O2 SENSOR SIGNAL BIASED/STUCK RICH BANK 1 SENSOR 2
2.CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and rear oxygen sensor.
3) Measure the resistance of harness between ECM connector and rear oxygen sensor connector.
Connector & terminal
(E158) No. 56 — (E25) No. 4:
(E158) No. 57 — (E25) No. 3:		Is the resistance less than 1 --Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P2271 O2 SENSOR SIGNAL BIASED/STUCK RICH BANK 1 SENSOR 2Repair the open circuit of harness between ECM connector and rear oxygen sensor connector.
3.CHECK HARNESS BETWEEN ECM AND REAR OXYGEN SENSOR CONNECTOR.
Measure the resistance between the ECM connector and engine ground.
Connector & terminal
(E158) No. 56 — Engine ground:		Is the resistance 1 M- or more-Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P2271 O2 SENSOR SIGNAL BIASED/STUCK RICH BANK 1 SENSOR 2Repair the short circuit to ground in harness between ECM connector and rear oxygen sensor connector.
4.CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
• Looseness and improper fitting of exhaust system parts
• Damage (crack, hole etc.) of parts
• Damage (crack, hole etc.) 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. Rear Oxygen Sensor
1. OUTLINE OF DIAGNOSIS
Detect the stuck of rear oxygen sensor voltage in rich state.
Detect the stuck in rich state and judge as NG if rear oxygen sensor voltage remains above the threshold value for predetermined time.
2. COMPONENT DESCRIPTION

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(A)Electromotive force(B)Air fuel ratio(C)Lean
(D)Rich(E)Theoretical air fuel ratio(F)Comparative voltage
3. EXECUTION CONDITION
















Secondary ParametersExecution condition
Battery voltage≥ 10.9 V
Fuel cut time≥ 5000 ms
Estimated temperature of the rear oxygen sensor element≥ 500 °C (932 °F)
4. GENERAL DRIVING CYCLE
Perform the diagnosis only once after the enable conditions have been established.
5. DIAGNOSTIC METHOD
If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.
Judgment Value








Malfunction CriteriaThreshold Value
Output voltage of rear oxygen sensor> 0.15 V
Time Needed for Diagnosis: 500 ms
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.




DTC DETECTING CONDITION:Immediately at fault recognitionCAUTION:After servicing or replacing faulty parts, perform Clear Memory Mode Clear Memory Mode > OPERATION, and Inspection Mode Inspection Mod ...


DTC DETECTING CONDITION:Detected when two consecutive driving cycles with fault occur.CAUTION:After servicing or replacing faulty parts, perform Clear Memory Mode Clear Memory Mode > OPERATION, and I ...


Other materials:

1. Place the back plate - rear brake between the housing assembly - rear axle and the hub unit COMPL - rear axle, and tighten the bolt.CAUTION:• Do not get closer the tool which charged magnetism to magnetic encoder.• Be careful not to damage the magnetic encoder.Tightening torque:65 N&m ...