A/F Sensor Heater Circuit Open/Short Inspection

Fig 1: Identifying A/F Sensor, PCM And Main Fuse Block Connector Terminals

Courtesy of MAZDA MOTORS CORP.

1. Disconnect the PCM connector.
2. Disconnect the A/F sensor connector.
3. Inspect the following wiring harnesses for an open or short circuit. (Continuity inspection)

Open circuit 

• If there is no continuity, there is an open circuit. Repair or replace the wiring harness.

• A/F sensor terminal C and main relay terminal C
• A/F sensor terminal D and PCM terminal 2BG

Short circuit 

• If there is no continuity, there is a short circuit. Repair or replace the wiring harness.

• A/F sensor terminal C and body ground
• A/F sensor terminal D and power supply
• A/F sensor terminal D and body ground