I've been reading for hours on this and it's hard to get a clear answer...

I installed new pipes and high flow air cleaner, had the bike tuned at HD via a download. Worked good for 10 min, then I get a check engine light and the error codes :

P0151 Rear Oxygen Sensor Low

P0154 Rear Oxygen Sensor Inactive

bike still runs ok but I want to fix this. I did not put new pipe gaskets, just reused the originals, so I am considering a leak but Does anyone have a suggestion?

thanks

 

Check the wiring to the rear O2 sensor has not been damaged or has come unplugged.

If it is a Softail then the connector for the rear is under the oil tank and a bitch to get to.

Easier to remove the battery and go through the bottom of the battery box.

Other models just follow the wire and see what you find.

 

The wiring was the first thing I checked, everything is connected.

 

Perhaps swap the front to the rear and the rear to the front and see if the problems moves with it.
If it does then it probably is a bad/damaged sensor.
I have seen them get damaged during removal if they were tight.

 

My first guess would be you have a leak on one pipe and you crushed the wrap on the connector on the other cutting off the reference air supply. I can't really decide which would be which.

 

So it ran for a little while.
Maybe the exhaust gasket loose.
Maybe O2 sensor wire burned.
Something like said. gotta check it out.