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 "Power Circuit Inspection" procedure.

IG "OFF" & Disconnect HO2S(B1/S1) connector.

IG "ON".

Measure voltage between power terminal of HO2S(B1/S1) heater harness connector and chassis ground.

Is the measured voltage within specification ?

	▶ Go to "Control Circuit Inspection" procedure.
	▶ Repair open or short to ground in HO2S(B1/S1) Heater power circuit then, go to "Verification of Vehicle Repair" procedure.

IG "OFF" & Disconnect HO2S(B1/S1) connector.

Measure resistance between control terminal of HO2S(B1/S1) heater harness connector and chassis ground.

Is the measured resistance within specification ?

	▶ Go to "Control Circuit Inspection" procedure.
	▶ Repair short to ground in HO2S (B1/S1) heater control circuit and go to "Verification of Vehicle Repair" procedure.

IG "OFF" and disconnect HO2S(B1/S1) and ECM connector.

Measure resistance between control terminal of HO2S(B1/S1) heater harness connector and heater control terminal of ECM harness connector.

Is the measured resistance within specification ?

	▶ Go to "Component Inspection" procedure.
	▶ Repair open in HO2S(B1/S1) heater control circuit and go to "Verifiction of Vehicle Repair" procedure.