I tried to get my car smogged in April in CA, but it needed a new mass flow sensor. So I had my mechanic install one. Since then I have driven almost 800 miles making sure to drive many many complete driving cycles. But the “Not Ready” flag for my O2 sensor still shows red. What should I do next? Replace the O2 sensors? None of the local auto mechanics seem to have a clue.
Test the function of the suspected O2 sensor. Replace the sensor if it fails.
Driving Cycle Pattern
- Start Engine when temperature is below 95 F degrees.
- Keep engine idling till engine coolant temperature has reached 158 F degrees.
- While Driving, Depress the the accelerator pedal until the vehicle speed is 56 MPH, then release the accelerator pedal and keep it released for more than 10 seconds. Depress the accelerator pedal until the vehicle speed is 56 MPH again.
- Time required may vary based on road conditions, weather, altitude, individual driving habits, etc.
Oxygen Sensor (O2S) Visual Inspection
The oxygen sensor is installed in the exhaust system and monitors the oxygen content of the exhaust gases. A voltage signal from the sensor informs the powertrain control module (PCM) as to the exhaust gas oxygen content (lean or rich condition). The PCM will interpret the voltage signal and compensate for the indicated condition.
The oxygen sensor should be inspected for proper installation and electrical connection. It should be noted that some vehicles are equipped with more than one oxygen sensor.