April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0134: A/F/O2 Sensor Circuit No Activity Detected Bank 1 Sensor 1: Notes

DTC detecting condition:

Immediately at fault recognition

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

G16446233

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .

NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR (OPEN) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connector from the front oxygen (A/F) sensor.
4. Measure the resistance of harness between ECM connector and front oxygen (A/F) sensor connector.
  Connector & terminal
  
  (E158) No. 52 - (E24) No. 1:
  
  (E158) No. 51 - (E24) No. 4:
  
  (E158) No. 53 - (E24) No. 5:
Is the resistance less than 1 Ω?

Yes: Go to 2.

No: Repair the open circuit of harness between ECM connector and front oxygen (A/F) sensor connector.
CHECK FOR POOR CONTACT .
Check for poor contact of ECM and front oxygen (A/F) sensor connector.

Is there poor contact of ECM or front oxygen (A/F) sensor connector?

Yes: Repair the poor contact of ECM or front oxygen (A/F) sensor connector.

No: Replace the front oxygen (A/F) sensor. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>FRONT OXYGEN (A/F) SENSOR .