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.

Has a problem been found?

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

IG KEY "OFF".

Disconnect HO2S(S1)_UP connector.

IG KEY "ON" & ENG "OFF"

Measure the voltage between Virtual Ground terminal "3" of HO2S(S1)_UP harness connector and chassis ground.

Measure the voltage between Nernst Voltage terminal "1" of HO2S(S1)_UPharness connector and chassis ground.

Measure the voltage between Current Pump terminal "1" of HO2S(S1)_UP harness connector and chassis ground.

Measure the voltage between Trim Resistor terminal "4" of HO2S(S1)_UP harness connector and chassis ground.

Is the measured voltage within specification ?

	▶ Go to "Component Inspection" procedure.
	▶ Repair Open or Short circuit and then, go to "Verification of Vehicle Repair" procedure.