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Bad 02 Sensor


Ed Hall

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My gas mileage has been very low and I had a P042 code (Left Oxygen Sensor Signal Lean). I cleaned all the carbon out of the phenolic spacers and now the p042 code is gone but now I get a p046 code (Right to Left Bank Fueling Difference). I went into the onboard computer and the left O2 sensor is reading a steady 0.05 which means it is either bad or has a bad connection.

Several months ago, the radiator cracked in this location and I think some antifreeze got onto the 02 sensor. Would antifreeze ruin an 02 sensor? I'm going to check the connection first before buying a new sensor. Does antifreeze have silicone in it? I heard that silicone destroys 02 sensors.

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I just posted about the same thing. My water pump was leaking coolant onto the exhaust manifold 02 sensor. Suddenly one evening with all the water constantly hitting the sensor the engine began to idle rough and a code popped up about uneven reading between bank 1 and 2. I think the antifreeze may have damaged the 02 sensor. Well, everything seemed to get better with time--It seemed the 02 sensor problem cleared up because the engine is idling almost as good as before. However, gas mileage is not as good as before the water pump problem. So yesterday I ordered a new ACDelco 02 sensor from AutoPartsGiant.com.

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Looks like my 02 sensor is deader than a doornail. This evening, I checked the connection at the plug and it looked fine. And of course as I separated the plug, the plastic tabs broke. Eventhough the car has low miles, age and heat has caused the plastic plug to become brittle. Once I get my new sensor, I'll have to use a tie wrap to keep it together. The part costs about $45 from Rockauto which is much cheaper than my friend who paid $300 for the 02 sensor on his fairly new Lexus ES300.

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Update: All fixed

My Delco O2 sensor that I ordered from Rockauto came in yesterday so I got it installed. No code comes up anymore and the onboard computer shows readings on that sensor other than 0 so it's working. I noticed that my instantaneous mileage especially around town is significantly higher. It used to be that when I let off the throttle at 60 mph, the instantaneous mileage would go up to about 40, now it goes to 70. The onboard computer on these cars are awesome for diagnosing problems for a shadetree mechanic like me.

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