I'm gettin a P0152 code occasionally. '07 FLHTCU. Rear O2 sensor rich. Had the code when I originally purchased the bike back in early July. I cleared it, I usually check it after every ride. Was okay until today, got it again. CEL, not illuminated. Since getting the bike I have replaced the air filter, spark plugs, and all three oils, not sure what to think about this, I do have an extended warranty just want to make sure I'm not harming anything. Seems that running rich would be a better condition than running lean. There is no black smoke to indicate a really excessively rich condition. Everything there seems normal as well. I have pulled the plugs to check the condition, if anything they look like they're running on the lean side rather than rich. At 74 years of age my hot rodding days are pretty much over, I'm pretty gentle on the bike. I do a lot of engine braking downshifting quite a bit don't know if that has any bearing on anything. With all the hills around this neck of the woods I am rarely in sixth gear mostly fifth, usually downshift if RPM falls below 2000 RPM.. So I don't think I'm lugging it to any degree. No pinging, bike runs great, just concerned about the continued appearance of the 0152 code. This is my first FI bike, pretty steep learning curve for an old guy! Would this be considered a normal occurrence on these FI bikes? No other codes are present. I have no reservations about going into dealer to have them look at it, it's just that it's a 75 mile jaunt. If it's something I can handle here myself I just as soon do it, or as long as isn't harming anything I'll just let it go until I store it in ? Judging by the way the maples are beginning to turn at this early date that could be any day!!

 

If the plugs look good, I would suspect a bad O2 sensor, or a fault in the wiring. Check the connection to the O2 sensor, and the connection on the other end of the cable. If both check out then look at the cable for problems.

If everything looks good, it's most likely a bad sensor.

 

Anyway to check the wiring, aside from a visual inspection. I have the electronic troubleshooting manual, but it appears a breakout box is required to do any comprehensive checks. Don't have the sensor socket either to remove the O2 sensor. Sounds like a dealer trip! As I'm sitting here thinking about it, I did wash the bike yesterday, and as I recall the connection for the O2 sensor is underneath the starter. I'll take a look at that if I can pull it apart. Looks tough to get to.