Cummins ISB CM850 (2003-06) Fault Code: 2976 PID: SPN: 3361 FMI: 2 Dosing Control Unit Temperature – Data Erratic, Intermittent, or Incorrect. An internal error has been detected in the catalyst dosing control unit.

Posted by PerDiezel Solutions on January 18, 2026

Fault Code 2976 is triggered when the dosing control unit internal temperature sensor is reading a different value than the other temperature sensors on the engine. This indicates a problem with the internal temperature sensor of the dosing control unit. Dosing control unit electrical supply issues that cause the dosing control unit to remain powered when the key switch is turned OFF can cause Fault Code 2976 to become active.

On-Board Diagnostics (OBD) Information (Euro 4.5 Certified Engines):

1)The ECM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2)An engine torque derate will be activated after 50 hours of engine operation with the fault code active.
3)To validate the repair and turn off the MIL, the engine must be shut down with the keyswitch in the OFF position for a minimum of 8 hours. After the 8 hour cold soak, if the ambient temperature is below 2?C [36?F] or above 25?C [77?F] start the engine and allow it to idle for 1 minute or run the diagnostic. If these temperatures can not be achieved, calibrate the EMC to the latest version found in the calibration revisions listed in the ECM Calibration Revision History.
4)The ECM turns OFF the MIL after 1 ignition cycle that the diagnostic runs and does not fail. The MIL lamp can not be cleared with INSITE? electronic service tool. The fault code will be cleared from memory after 400 days or 9,600 hours of engine operation.

Possible repairs:

1)Replace the DEF dosing unit if damage is detected.
2)Repair or replace the OEM harness.
3)Replace the aftertreatment DEF dosing unit.
4)If necessary, calibrate the ECM.

Cummins ISB CM850 (2003-06) Fault Code: 2973 PID: 102 SPN: 102 FMI: 2 Intake Manifold Pressure Sensor Circuit – Data Erratic, Intermittent, or Incorrect. The electronic control module (ECM) has detected an intake manifold pressure signal that is too high or too low for present engine operating conditions.

Cummins ISB CM850 (2003-06) Fault Code: 2964 PID: 105 SPN: 105 FMI: 15 Intake Manifold Temperature High – Data Valid But Above Normal Operating Range – Least Severe Level. Intake manifold air temperature signal indicates intake manifold air temperature above engine protection warning limit.

Cummins ISB CM850 (2003-06) Fault Code: 2963 PID: 110 SPN: 110 FMI: 15 Engine Coolant Temperature High – Data Valid but Above Normal Operational Range – Least Severe Level. Engine coolant temperature signal indicates coolant temperature is above the engine coolant temperature engine protection warning limit.

Cummins ISB CM850 (2003-06) Fault Code: 2962 PID: 412 SPN: 412 FMI: 0 EGR Temperature – Data Valid But Above Normal Operating Range, Moderately Severe Level.

Cummins ISB CM850 (2003-06) Fault Code: 2961 PID: 412 SPN: 412 FMI: 15 Exhaust Gas Recirculation (EGR) temperature – Data Valid but Above Normal Operating Range, Least Severe Level.

Cummins ISB CM850 (2003-06) Fault Code: 2773 PID: SPN: 3226 FMI: 0 Aftertreatment Outlet NOx – Data Valid but Above Normal Operational Range – Most Severe Level. The engine NOx output is higher than recommended levels.

WARNING!