HO2S Circuit Open/Short Inspection

Fig 1: Identifying HO2S Wiring Harness-Side Connector Terminals

Courtesy of MAZDA MOTORS CORP.

1. Disconnect the PCM connector.
2. Disconnect the HO2S connector.
3. Inspect the following wiring harnesses for an open or short circuit. (Continuity inspection)
   Fig 2: Identifying PCM Wiring Harness-Side Connector Terminals

   Courtesy of MAZDA MOTORS CORP.

Open circuit 

• If there is no continuity, there is an open circuit. Repair or replace the wiring harness.
  • HO2S terminal A and PCM terminal 2Q
  • HO2S terminal B and PCM terminal 2BH
  • HO2S terminal C and ignition relay
  • HO2S terminal D and PCM terminal 2BE

Short circuit 

• If there is continuity in the following wiring harnesses, there is a short circuit. Repair or replace the wiring harness.
  • HO2S terminal A and power supply
  • HO2S terminal A and body ground
  • HO2S terminal B and power supply
  • HO2S terminal B and body ground
  • HO2S terminal C and body ground
  • HO2S terminal D and power supply
  • HO2S terminal D and body ground