Common trouble codes for Harley motorcycles are P codes, which indicate issues monitored by the electronic control module, and B codes, which indicate problems with the radio, instruments or body control module. C codes are issues related to the braking system, and U codes indicate communication problems. A full list of Harley trouble codes is available in the service manuals on the official Harley Davidson website.
P codes that may occur in Harley Davidson motorcycles manufactured after 2008 include P0131, which indicates that the front oxygen sensor is emitting a low reading, P0132, which shows a high reading, and P0134, which means the sensor is inactive. One B code is B1135, an accelerometer fault within the turn signal or turn signal security module. C1043 is an error code that indicates that the pump motor has stalled. U1097 indicates that there is a loss of data between the speedometer and the electronic control module.
To run a diagnostic check on a Harley to determine the presence of a fault, place the ignition in the OFF position, and the Run/Stop switch needs to indicate Run. Pressing and holding the odometer reset button, turning the ignition switch on, and releasing the button should start the diagnostic process. Background lights should illuminate, the speedometer should do a full sweep and the word “Diag” should appear. Pressing the odometer reset button again brings up the diagnostic menu. The flashing letter is the module that is checked. P is the electronic control module and ignition control module, S is the turn signal and security section, SP indicates speedometer diagnostics, and T represents tachometer.