Harley Cruise Control Diagnostics

If your Harley cruise control has an issue, there is an interactive cruise diagnostic test that can be performed on the motorcycle without the need or aid of any diagnostic service scan tools or computer.

The Harley cruise control function is governed by the motorcycle’s ECM. The ECM monitors the vehicle speed sensor (VSS) to establish the bike’s current speed. The ECM then modulates the throttle control actuator to maintain a constant vehicle speed. When cruise control is enabled, the orange cruise lamp will change to green. The ECM monitors the engine RPM and the output signal from the vehicle speed sensor. Then, the ECM signals the throttle control actuator to open or close the throttle to keep the speedometer output speed signal constant.

The ECM will automatically disengage an active Harley cruise control mode if it receives one of the following input signals:

– Front brake is applied
– Rear brake is applied
– Throttle is rolled forward (throttle roll off/ cruise disengage command)
– Clutch lever is engaged
– Wheel slip is detected (an ECM detected jump in RPM)
– Pressing cruise switch
– SET/- switch is held in until the motorcycle speed drops below thirty miles per hour
– RESUME/+ switch is held in until motorcycle speed goes above ninety three miles per hour.

Bob and Mark give us a sequence demonstration for entering and moving through the cruise diagnostic mode. The illuminated amber/orange cruise light changes to green for every tested function.

If your Harley cruise control is not functioning correctly, you may have one of the following conditions to pursue:

– Throttle position faults P0120 & P0220
– Vehicle Speed Sensor faults P0501 & P0502
– Cruise control switch failure
– Front or Rear brake switch failure
– Throttle position error P2135
– Flash memory error P0605
– ETC limited performance mode

The most common reason for inoperative or intermittent cruise failure is from a broken or misaligned front brake switch. If your cruise is not working, look behind you. See if your brake light is stuck on. Could be an easy fix.