Thread: 2003 3.4 P0420 Post intake coolant leak
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Old 04-01-2012, 09:31 PM   #2
Tech II
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Re: 2003 3.4 P0420 Post intake coolant leak
That second O2 sensor should be going low and stay there and then go high, and stay, slowly changing high to low and back......it should not be staying near the middle.....either a bad sensor(contaminated by coolant?) or bad cat....
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