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Cummins X15 CM2350 X116B Performance Series (2018 & Newer) Fault Code: 5866 PID: SPN: 520953 FMI: 3/3 Aftertreatment Diesel Exhaust Fluid Dosing Unit Relay Feedback – Voltage Above Normal or Shorted to High Source

Lamp:
Amber

Reason:
A short to battery has been detected on the diesel exhaust fluid dosing unit relay feedback signal.

Effect:
Possible reduced engine performance.

Circuit Description:
The aftertreatment diesel exhaust fluid dosing unit performs many functions, one of which is to generate adequate diesel exhaust fluid pressure in the lines, using a pump, to allow for dosing. The ECM provides a battery voltage supply and a ground to the diesel exhaust fluid dosing unit. The ECM also supplies a signal to the dosing unit to control the diesel exhaust fluid output. This signal changes, based on the diesel exhaust fluid pressure being commanded.

Component Location:
The aftertreatment diesel exhaust fluid dosing unit location is Original Equipment Manufacturer (OEM) dependent.

Conditions for Running the Diagnostics:
This diagnostic runs when the aftertreatment diesel exhaust fluid dosing unit is commanded OFF.

Conditions for Setting the Fault Code:
The Engine Control Module (ECM) detected voltage above a calibrated value on the pump relay feedback circuit when the dosing valve was not commanded ON.

Action Taken When the Fault Code is Active:
1. The ECM will illuminate the maintenance lamp during the key cycle after the diagnostic runs and fails.
2. Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.

Conditions for Clearing the Fault Code:
To validate the repair, start the engine and let it idle for 1 minute.

Shop Talk:
Possible causes of this fault code include:
Short to battery or ground in the OEM harness.