I thought I'd share a recent experience I had with a DTC "P0131 Hist Oxygen sensor low/ engine lean Front" code on my 2016 Ultra Classic.

I was on a one week trip, about 1700 miles round trip, to Flagstaff (with multiple day rides around Flagstaff) and back to San Diego. I made the trip on my '16 Bagger, with a 124" Street Outlaw engine installed by FuelMoto and tuned by Jaime. It ended up @ 135HP & 151TQ. It's an absolute joy to tour on...

I knew we would be going through the desert at the beginning and end of the trip, which ended with me arriving home on 7/30/23. I knew it was going to be hot, so for the first time in my life, I wore a full face helmet (with speakers for my stereo) to ward off the sun... The vented helmet was cooler than riding with no helmet, or my usual half helmet, in the high heat and intense sun. I offer this info, because with the half helmet, I can't hear my engine like I can without it...

The trip went well, and the bike ran very well, with one small exception. I pulled into Laughlin, Nevada, my last stop before home, and it was 120°. At two short stop lights, just prior to my hotel, I could hear and feel the engine idling poorly and it just sounded strange. Other than those two stop lights, it ran well in the heat and on the rest of the way home.

The next day when we left early, it was still 100°, but the bike fired right up and made it home without incident.

That weird stoplight idle bothered me, so I checked the bike for codes and found the historical code listed above. I was going to write it off, since it was historical, to the high heat and some glitch at the stop lights.

I contacted FuelMoto about possible tune issues that could cause this, and Jaime told me to send him a datalog.

After viewing the datalog, he told me "something is going on with that front cylinder" and gave me several suggestions of things to check. His first one was that when he saw that kind of datalog activity, it was usually a failing O2 sensor, damaged sensor wiring/connector issue, or the O2 sensor had worked loose in the pipe, causing an air leak....

I put my bagger on the lift, before even cleaning it up, to check the sensor.

Jaime was right, an air leak was causing the DTC, but it wasn't a loose front O2 sensor. Here is what I found....









As you can see, there was a large crack in the front header pipe, just aft of the exhaust mount and the front O2 sensor. It was a pretty big crack, and I was surprised that when I checked for codes it was a historical code, not an active code.

I knew the exhaust was going to need to be welded or replaced, so I removed the exhaust from the bike. That quickly removed the possibility of welding the pipe, as the front header tube broke off in my hands...

This all ends well....... It was a FuelMoto exhaust (Jackpot Road & Track 2-1) that I bought from FuelMoto. I actually installed it on my OEM 103" engine, and kept the same exhaust when I added the 124" engine. The exhaust was purchased in 2018. A couple hours after sending pics to FuelMoto, I received an email & warranty receipt from Mikayla, and told that my new head pipe was being shipped... no charge..

As Jaime pointed out to me, and many of you know, that code can be caused by an exhaust air leak, a plugged fuel injector, or an intake leak. While I was aware of some of these possibilities even before Jaime graciously took the time to share them with me to resolve my DTC, I would never have thought it was a loose O2 sensor, or a cracked pipe.....

I hope my experience will help someone else who runs into a similar experience with an O2 sensor code.... check the pipe..!!!!

 

thanks for sharing.
just curious how you discovered it. were the covers on the head pipe when you discovered the crack.

 

Yes the heat shields were on.....

Jaime suggested the O2 sensors could get loose, causing an air leak.

I checked the O2 sensor was tight, but did it blind, by feel....

I felt the crack and it felt like a "seam".

I didn't remember a seam in that area of the head pipe, so I got my inspection mirror to give a look....

The crack was quite obvious in the inspection mirror..

 

I hope my experience will help someone else who runs into a similar experience.
I am glad you found the problem and are being taken care of, but I feel sorry for Fuel Motto as this seems to be an issue with the pipes and since they are so good with the warranty it will hurt. I hope it is a relatively small number of pipes that are affected and Fuel Motto gains more business.

 

I was commenting more on the DTC code diagnosis, and the need to check for air leaks right at the O2 sensor (loose O2 sensor or cracked pipe).

With the heat shields in place, I could have removed , checked, and/or replaced the O2 sensor without noticing that crack. Then I would have moved onto other possible causes and heaven knows how long it would have taken me to actually check the pipe and find the cause of that DTC .....

The crack looks to have started right at the weld on the mount. I read in another post about the same exhaust issue, that the updated RTX exhaust by FuelMoto has a different mount. I suspect the only warranty claims will be on older pipes, to the original owners.... I would guess that would be a smaller, manageable number...

I am a customer of FuelMoto since 2011. Whenever possible, I do business with them. IMHO, FuelMoto is a stand-up company, makes good products, and stands behind them.

I didn't want to just have an open ended comment about a broken FuelMoto head pipe in my thread... The warranty header replacement info was just an aside, to highlight FuelMoto's superior customer service...