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131/151 Historical Codes

The most common cause of 131/151 error codes on bikes with XiED's installed is the presence of exhaust leaks. Even the smallest exhaust leak can trigger this code.
  • For any bike with slip-on mufflers, this is the most likely situation. Loosen your muffler clamps so you can look for any wisps of carbon on both slots of your mufflers. Even the smallest wisp of carbon is an indication of a leak. The muffler must be properly installed on the OEM header pipes. We have also seen problems with the use of non-OEM muffler clamps.
  • More often on FLH based bikes, we also see the rear exhaust manifold gasket becoming loose or damaged. This is very common when new mufflers are installed. So make sure that the exhaust manifold flanges have proper torque applied to them.
  • On some new bikes or those with complete exhaust replacements, we have also seen the O2 sensor not properly tightened.
  • On bikes with crossovers, the cross-over gasket can become dislodged or move. This is very common if the header pipes are removed for any reason.
  • You should not see 131/151 codes on 2010/2011 Touring bikes.

Any or all of these conditions can exist on any bike. We have even seen some of these issues on bone stock bikes.

Identifying and repairing the exhaust leaks eliminates most of the 131/151 codes from occurring.

For riders that still have these codes occurring and are sure they have doubled checked for all exhaust leak possibilities and ruled this out as their cause of the codes, place contact Nightrider through our contact page, providing specific details about your bike. We are looking at several IED upgrades that might improve your bike.

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Getting 131/151 Codes?
-Parts listed on this site that alter fuel mixtures or replace OEM pollution control devices are for Race Only Purposes. Check with local regulations and laws to ensure compliance. In California, Race Only products must not be used on any vehicle that is registered or licensed for use on public roads.
- References to Harley-Davidson and H-D makes, models and other trademarks are for reference purposes only and do not constitute affiliation or endorsement by Harley-Davidson Inc.
-Air Fuel Ratio's (AFR) represented for these products are based on exhaust gas temperatures (EGT) of 1400-1500 F. Cooler EGT during startup, cooler weather or during some dyno testing with cooling fans can result in .5 to .8 leaner AFR's. This is normal due to the way unheated narrow band O2 sensors react to changing EGT's. The "hotter" the engine gets, the better the IED's actually work.
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