▶ Carefully re-do this troubleshooting guide steps.

▶ If no problems were found with the circuits or connectors, Replace the Upstream O2 Sensor and then go to "Verification of Vehicle Repair" procedure.

▶ Fault might be intermittent and caused either by poor contact in connectors or wiring harness, or it has been repaired and control module memory is not cleared yet. Thoroughly check terminal of battery, all connectors ( and connections) for looseness, bending, corrosion, contamination, deterioration, and/or damage.

▶ Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.