Disconnect the HO2S and PCM/ECM connectors and inspect for looseness, poor connection, bending, corrosion, contamination, deterioration or damage. Reconnect the connectors.

Connect the GDS and go to “Current Data”.

Monitor HO2S values in Current Data, check and wiggle the harness(es), connector(s), and terminal(s).

Any change in the values indicates a poor connection. Was a connector problem found?

	▶ Repair the connector. Go to "Verification of Vehicle Repair" procedure.
	▶ Go to next step as below.

Ignition "OFF"

Disconnect HO2S connector.

Ignition "ON" & Engine "OFF"

Measure voltage between power terminal of HO2S heater harness connector and chassis ground.

Is voltage within specification?

▶ Go to "Control Circuit Inspection" procedure

▶ Check for an open in the power supply circuit between the main relay and the HO2S. Especially check for "SENSOR2 FUSE 15A" is installed and not blown. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure. note HO2S must have a clean air reference to function properly. The air is obtained by way of the sensor wire(s). Do not attempt to repair the wire(s), connector, or the terminals.

Ignition "OFF"

Disconnect HO2S connector.

Ignition "ON" & Engine "OFF"

Measure voltage between Heater Power terminal of the HO2S harness connector and chassis ground.

Is voltage within specification?

▶ Go to "Control Circuit Inspection" procedure

▶ Check for an open in the power supply circuit between the main relay and the HO2S. Especially check for "15A Sensor 2 fuse" is installed and not blown. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure. note HO2S must have a clean air reference to function properly. The air is obtained by way of the sensor wire(s). Do not attempt to repair the wire(s), connector, or the terminals.

Ignition "OFF"

Disconnect HO2S connector.

Ignition "ON" & Engine "OFF"

Measure voltage between control terminal of HO2S heater harness connector and chassis ground.

Is voltage within specification?

	▶ Go to "Component Inspection" procedure.
	▶ Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure. note HO2S must have a clean air reference to function properly. The air is obtained by way of the sensor wire(s). Do not attempt to repair the wire(s), connector, or the terminals.

Ignition "OFF"

Disconnect HO2S connector.

Ignition "ON" & Engine "OFF"

Measure voltage between control terminal of HO2S heater harness connector and chassis ground.

Is voltage within specification?

	▶ Go to "Component Inspection" procedure.
	▶ Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure. note HO2S must have a clean air reference to function properly. The air is obtained by way of the sensor wire(s). Do not attempt to repair the wire(s), connector, or the terminals.