Circuit/System Testing

Ignition OFF, disconnect the harness connector at the HO2S 1.
Test for 1.8 to 3.4 ohms at 20°C (68°F) between the ignition 1 voltage circuit terminal 2 and the heater control circuit terminal 1 of the oxygen sensor.
- If not within the specified range, replace the HO2S 1.
Ignition ON, test for 3.4-3.6 volts between the HO2S 1 input circuit terminal 3 and ground.
- If greater than the specified range, test the HO2S 1 input circuit for a short to voltage. If the circuit tests normal, replace the PCM.
- If less than the specified range, test the HO2S 1 input circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the PCM.
Test for the following conditions:
- Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
- Splits, kinks, or improper connections at the vacuum hoses
- The fuel system operating pressure is incorrect-Refer to Fuel System Diagnosis .
- The fuel injectors are operating lean or rich-Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) .
- Vacuum leaks at the intake manifold, manifold fittings, or throttle body
- Faulty crankcase ventilation system-Refer to Crankcase Ventilation System Inspection/Diagnosis .
- A collapsed or restricted air intake duct and a restricted or dirty air filter
- The incorrect operation of the evaporative emission control system-Refer to Evaporative Emission Control System Diagnosis .
If all conditions test normal, replace the HO2S 1.