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I have a stepside red Sierra 1500. My check engine light came on a year ago and I replaced the downstream O2 sensor on the passenger side catalytic converter.

However one day later the light came back on. I looked under and the reputable mechanic shop is hired to do the job showed me the quality of their work. The sensor was dangling.

Unfortunately I was moving from Hawaii to Kentucky (am active Army) so did a bit of shade tree to get it shipped. Once here my brother in law reinstalled the sensor.

The light continues to come on. The sensor has had to be reinstalled three more times since. I’ve not off roadbed it or done anything too crazy with it and it’s the best running vehicle I’ve ever owned. Since 2011 this sensor, the heater blower motor piece and the alternator are all I’ve had to replace outside of normal maintenance.

How do I fix this?

By the way, I’m Don and I own 3 GMC vehicles:

1997 GMC Sierra 4.3L V6 2WD
1999 GMC Jimmy 4.3L V6 4WD
2004 GMC Sierra step side 5.3L V8

All automatic transmission (only because I can’t find a manual anywhere)
 

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post the codes that helps, there is NO one O2 sensor code ..

I assume you have a cat efficiency code failure .. what you do is swap the down stream O2 sensors see if code comes back.

another issue if this is my guess on code after market cat converters will also do it .

using a scan tool that will show graphic of O2 sensor voltages the downstream O2 sensors have to shift from high to low at a slow rate compared to the upstream O2 ... if these are locked up not changing then the converter is not reacting to the fuel ratio changes ..
 

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Don, these sensors are threaded, if it won't stay inserted eithe the sensor or the sensor bung is stripped.
The proper fix would be to replace the stripped portion.
Either a new sensor, or weld in a new bung.
 

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The issue is that the new sensor will not stay inserted
are you the person installing this ? if a shop did it , why is it they did not fix the threads on the pipe ?

most times the issue is the threads are rusted distorted and you use a plug thread chaser . then install the O2 sensor .

the O2 sensor does require a solid electrical bond to the pipe fitting.. so any locktite may mess up the sensor output.

never heard of this problem of sensor popping out ... someone must of cross threaded the hole or used a torch on the pipe damaging the threads.

possible the pipe is aftermarket that would explain why its not holding in place..
 
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