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

1. -

DTC detecting condition:

Immediately at fault recognition

Wiring diagram:

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

G13626787

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>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) (H4DO)>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 and terminal
  
  (E53) No. 3 - (B94) No. 3:
  
  (E53) No. 4 - (B94) No. 4:
  
  Is the resistance less than 1 Ω?
  
  Yes : Go to 2 .
  
  No : Repair the following item.
  - Open circuit in harness between ECM connector and front oxygen (A/F) sensor connector
  - Poor contact of coupling 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) (H4DO)>FRONT OXYGEN (A/F) SENSOR .