Circuit/System Testing

Ignition OFF, disconnect the harness connector at the HO2S 2.
Ignition OFF, test for less than 10 Ω between the low reference circuit terminal 3 and ground G104.
- If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the PCM.
Ignition ON, observe the scan tool HO2S 2 voltage parameter. Verify the HO2S reading is between 35-55 mV.
- If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the PCM.
Connect the test lamp between B+ and the HO2S 2 signal circuit terminal 4.
Ignition ON, verify the scan tool HO2S 2 voltage is greater than 1,125 mV.
- If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM.
Verify that none of the following conditions exist:
- 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) .
- Missing, restricted, or leaking exhaust components-Refer to Exhaust Leakage .
- Vacuum leaks at the intake manifold, manifold fittings, or throttle body - P0171
- 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 - P0172
- Excessive fuel in the crankcase - P0172
- The incorrect operation of the evaporative emission control system-Refer to Evaporative Emission Control System Diagnosis .
Engine running at normal operating temperature, observe the scan tool HO2S 1 voltage parameters listed below while commanding the fuel injector rich or lean with the scan tool.
- Command the Fuel Injector Modification Commanded State to +25 percent - The HO2S 1 voltage should decrease to less than 3.0 V.
- Command the Fuel Injector Modification Commanded State to -11 percent - The HO2S 1 voltage parameter should increase to greater than 3.35 V.
- Command the Fuel Injector Modification Commanded State to 0 percent - The HO2S 1 voltage parameter should fluctuate between 3.2-3.4 V.
- If the scan tool HO2S 1 voltage parameter was not within the specified ranges, replace the HO2S 1.
If all the tests are normal, replace the HO2S 2.