Hi,
Ann, the drive cycle won't turn the light off. There are several monitors that watch what is happening with different circuits. Once the codes are cleared, you must then drive it until the monitors are reset. If the check engine light stays off, you are good to go. The only way to confirm that is with a scan tool to see if it is ready for testing. On the other hand, if the light is still on, there is still a problem.
When you indicated the o2 sensors didn't move as far as voltage, there should be a difference between the up and down-stream sensors. You should see the voltages change when the engine demand changes such as when you hit the throttle. If that isn't happening and both are showing similar readings (sensors 1 and 2) the catalytic converter is likely failing.
Since the catalytic converter is in question, you can check it with an infrared thermometer. Take a look through this link that explains how to test one:
https://www.2carpros.com/articles/how-to-test-a-catalytic-converter
When you check the temperature, the outlet of the converter should be hotter than the inlet.
Let me know if the code or codes you have are P0420 or P0430.
Joe
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Wednesday, June 26th, 2024 AT 9:03 PM