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Q: How hard is it to change the O2 sensors?

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All four oxygen sensors show to be bad on diagnostic tool of the mechanic who installed my used 2005 Ford Escape 6cyl engine. He said it is due to the used engine sitting up and then blowing out carbon build up, messing up the O2 sensors. Is this accurate? I read that sometimes O2 sensors show to be bad if there is any leak in the exhaust system.
My car has an automatic transmission.

Hello. I have never seen all four oxygen sensors go bad on a vehicle all at one time. They will fail one at a time and the only time it would need all four would be if they failed one at a time and were never replaced. It is very common to get oxygen sensor codes when there is something else going on with the engine or the exhaust. I usually see what the sensors are doing on a scan tool and then check and see if the issue can be ignition or fuel related. If you need to have these oxygen sensors checked out, consider having a technician from YourMechanic come to your home or office to diagnose the problem and replace the oxygen sensors if needed.

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