Cummins ISB6.7 CM2350 (2013-17) Fault Code: 1866 PID: 411 SPN: 411 FMI: 2 Exhaust Gas Recirculation Differential Pressure- Data Erratic, Intermittent, or Incorrect

Circuit Description
The exhaust gas recirculation (EGR) differential pressure sensor has two ports that sense exhaust pressure. The sensor outputs a voltage which represents the pressure difference between the two ports located across an orifice in the EGR tube. The engine control module (ECM) uses this pressure to determine how much exhaust gas is flowing in the EGR connection tube to the intake manifold. This information is used to control the EGR valve for correct emission levels.The ECM provides a 5 volt supply to the EGR differential pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The EGR differential pressure sensor provides a signal to the ECM on the EGR differential pressure sensor signal circuit. This sensor signal voltage changes, based on the differential pressure in the EGR crossover tube.The EGR differential pressure sensor measures the exhaust gas pressure drop across the EGR differential pressure orifice. This pressure drop is used to calculate the amount of EGR flow into the intake manifold.

Component Location
The EGR differential pressure sensor is mounted on the EGR mass measurement assembly.

Conditions for Running the Diagnostics
1)This diagnostic runs at key OFF when the following conditions are met:
2)Engine coolant temperature is 68?C [154?F] or higher.
3)Intake manifold air temperature is 7?C [44?F] or higher.
4)Keyswitch transitions from ON to OFF.

Conditions for Setting the Fault Codes
The Engine Control Module (ECM) detected the EGR differential pressure sensor was reading higher or lower than a calibratable value when the keyswitch was turned OFF.

Action Taken When the Fault Code is Active
1)The ECM illuminates the amber CHECK ENGINE lamp and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.
2)Diesel exhaust fluid injection into the aftertreatment system is disabled.
3)Active and stationary regeneration of the diesel particulate filter will be disabled.
4)Exhaust Gas Recirculation (EGR) valve operation will be disabled.
5)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
1)To validate the repair, first ensure the engine coolant temperature is above 70?C or 158?F. Operate the engine if necessary.
2)The keyswitch must be completely turned OFF for more than 30 seconds before this diagnostic will run at initial key ON.
3)The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
For On-Board Diagnostics (OBD) engines, the ECM will extinguish the Malfunction Indicator Lamp (MIL) after three consecutive trips where the diagnostic runs and passes.

Shop Talk
This check is only performed at keyswitch OFF, during the ECM powerdown. During this diagnostic check, the ECM monitors the value of the EGR differential pressure sensor. If this value is outside of a specified range, Fault Code 1866 is set active.

Possible causes:
1) A damaged EGR differential pressure sensor.
2) High resistance in the wiring harness on the signal or return wire.
3) Plugged or restricted EGR differential pressure sensor flow ports.