Cummins X12 CM2350 X119B (2018 & Newer) Fault Code: 7935 PID: SPN: 412 FMI: 10/10 Engine Exhaust Gas Recirculation 1 Temperature – Abnormal Rate of Change

Lamp:
Amber

Reason:
The EGR temperature sensor is reading an erratic value at initial key ON or while the engine is running.

Effect:
Possible reduced engine performance.

Circuit Description:
The Exhaust Gas Recirculation (EGR) temperature sensor is a variable resistor sensor and is used to measure the temperature of the EGR gas flow after it exits the EGR cooler. The Engine Control Module (ECM) supplies 5 volts to the EGR temperature signal circuit. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the EGR flow temperature.
The EGR temperature value is used by the ECM for the engine protection system and engine emissions control.

Component Location:
The EGR temperature sensor is located on the EGR connection tube between the EGR cooler and the air intake connection.

Conditions for Running the Diagnostic:
The engine must be turned OFF for period of 8 hours before this diagnostic will run. This diagnostic runs when the keyswitch is turned to the ON position after an 8 hour cold soak.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the EGR temperature reading was higher or lower than the other temperature sensors on the engine after an extended period of engine off time.

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, the engine must be shut down with the keyswitch in the OFF position for 8 hours. After the 8 hour cold soak turn the keyswitch to the ON position for 30 seconds.
2. The fault code status displayed by the recommended diagnostic tool or equivalent will change to inactive immediately after the diagnostic runs and passes.
3. The ECM will turn off the amber check engine lamp immediately after the diagnostic runs and passes.
4. 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.
5. The “reset all faults” command in the recommended diagnostic tool or equivalent can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk:
Possible causes of this fault code include:
1. Stuck in-range EGR temperature sensor.
2. High resistance in the EGR temperature sensor signal or return wires.