Cummins X12 CM2350 X119B (2018 & Newer) Fault Code: 7861 PID: SPN: 1172 FMI: 10/10 Turbocharger 1 Compressor Intake Temperature Sensor – Abnormal Rate of Change

Lamp:
Amber

Reason:
A temperature too high or low for the operating conditions has been detected by the turbocharger compressor intake temperature sensor.

Effect:
Possible reduced engine performance.

Circuit Description:
The turbocharger compressor intake temperature sensor is a variable resistor sensor and is used to measure the temperature of the air entering the compressor intake of the turbocharger. The Engine Control Module (ECM) supplies 5-VDC to the compressor intake temperature signal circuit. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the air temperature.

Component Location:
The turbocharger compressor intake temperature sensor is located in the compressor inlet of the turbocharger.

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 compressor intake temperature reading was higher or lower than other temperature sensors after 8 hours(engine off), or the sensor reading is erratic during engine running.

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. A default value for the compressor intake temperature reading is used.
3. Diesel exhaust fluid injection into the aftertreatment system is disabled.
4. Active and stationary regeneration of the diesel particulate filter will be disabled.
5. Exhaust Gas Recirculation (EGR) valve operation will be disabled.
6. 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 compressor intake temperature sensor.
2. High resistance in the compressor intake temperature sensor signal or return lines.
3. ECM malfunction.