A/F Sensor Circuit Open/Short Inspection

1. Disconnect the PCM connector. (See PCM REMOVAL/INSTALLATION ).
2. Disconnect the A/F sensor connector.
3. Inspect the following wiring harnesses for an open or short circuit. (Continuity inspection)
   Fig 1: PCM Connector Terminal Identification

   Courtesy of MAZDA MOTORS CORP.
   Fig 2: Identifying PCM Wiring Harness-Side Connector Terminals

   Courtesy of MAZDA MOTORS CORP.

Open circuit 

• If there is no continuity in the following wiring harnesses, there is an open circuit. Repair or replace the wiring harness.
  • A/F sensor terminal A and PCM terminal 2AD
  • A/F sensor terminal B and PCM terminal 2Z
  • A/F sensor terminal C ignition relay
  • A/F sensor terminal D and PCM terminal 2BG

Short circuit 

• If there is continuity in the following wiring harnesses, there is a short circuit. Repair or replace the wiring harness.
  • A/F sensor terminal A and power supply
  • A/F sensor terminal A and body ground
  • A/F sensor terminal B and power supply
  • A/F sensor terminal B and body ground
  • A/F sensor terminal C and body ground
  • A/F sensor terminal D and power supply
  • A/F sensor terminal D and body ground