Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.

Have any problems been found?

	▶ Repair as necessary and go to "Verification of vehicle Repair" procedure.
	▶ Go to "O2 Sensor 1 Circuit Inspection" procedure.

Ignition "OFF" & Disconnect O2 sensor 1 connector.

Ignition "ON".

Measure voltage between Pin No. 1 (Nernst Voltage) terminal of O2 Sensor 1 harness connector and chassis ground.

Measure voltage between Pin No. 3 (Virtual Ground) terminal of O2 Sensor 1 harness connector and chassis ground.

Measure voltage between Pin No. 4 (Trim Resistor) terminal of O2 Sensor 1 harness connector and chassis ground.

Measure voltage between Pin No. 6 (Pumping Current) terminal of O2 Sensor 1 harness connector and chassis ground.

Are the measured voltages within specification?

	▶ Go to "System Inspection" procedure.
	▶ Repair or replace as necessary and then, go to "Verification of Vehicle Repair" procedue.