Seems like since the heat of summer left I get a 0139 code which usually translates as "O2 circuit slow response bank 1 sensor 2." Just pops up every now and then. Usually when I have random issues I figure it may be a connection or wiring. I also read that an exhaust leak can trigger it and I do think there may be one but it is upstream where the pipe connects to the manifold, on cold mornings I can hear it at start up but then it sounds normal as soon as the pipe and fitting warm up. Going to try to get under the car this weekend.

Thoughts?

 

Cracked flange on the y-pipe for the noise. Might be responsible for the code. Mine likes to throw that code too, but I just welded the flange up. I need to check the connector, then maybe try a different O2 sensor. I installed some pro-lines a few months ago that the PO threw in when I bought the truck. They might be crap.

 

I misread your post. I have been getting a P0130 code which indicates that the upstream O2 sensor is shorted or not reading. I checked it with my scanner and it was reading 0 volts. I pulled the connector apart and found it had gotten soaked in coolant at some point, likely when I tore down the motor to replace the head gaskets. I sprayed the connector with cleaner then blew it dry with air and so far no more codes.


A P0139 is for the post-cat O2 sensor. I was getting that code before I welded up my flange but since then I haven't had it pop up. I had a P0159 previously when the nuts on the passenger side had loosened up and the joint was leaking over there so it is likely that any leaks upstream of the convertors will trigger those codes.