Possible Cause
| Possible Cause | Cause check |
|---|---|
| 1. Poor contact of the Upstream oxygen sensor connector | Check connector fastening and contact failure Disconnect and check the connector for moisture inflow, foreign matter, bent terminal, pushed connector |
| 2. Defective Upstream oxygen sensor | Resistance measurement to check internal coil breakage and defects |
| 3. Defective Upstream oxygen sensor circuit | signal circuit check |