Cummins ISB4.5 CM2150 Fault Code: 1848 PID: 105 SPN: 105 FMI: 10 Intake Manifold 1 Temperature – Abnormal Rate of Change.

Circuit Description
The intake manifold 1 temperature sensor is a variable resistor sensor and is used to measure the temperature of the air entering the intake manifold of the engine. The engine intake manifold temperature value is used by the ECM for the engine protection system and engine emission control. The engine control module (ECM) supplies 5 volts to the intake manifold temperature signal circuit, and monitors the change in voltage caused by changes in the resistance of the sensor to determine the intake manifold temperature. When the intake air is cold, the sensor (or thermistor) resistance is high. The ECM signal voltage only pulls down a small amount through the sensor to a ground. Therefore, the ECM senses a high signal voltage, a low temperature. When the intake air is warm, the sensor resistance is low. The signal voltage pulls down a large amount. Therefore, the ECM senses a low signal voltage, or a high temperature.

Component Location
The engine intake manifold temperature sensor is located in the air intake manifold.

Conditions for Running the Diagnostics
The engine intake manifold temperature is monitored during engine warm-up. The ECM must not see engine speed for a period of 8 hours before this diagnostic will run.

Conditions for Setting the Fault Codes
The engine intake manifold temperature is monitored during engine warm-up. If the engine intake manifold temperature reading is not changing to match the engine operating conditions, the intake manifold temperature sensor is then determined to be stuck in-range and this fault code is logged.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp and immediately when the diagnostic runs and fails.
-The ECM will estimate engine intake manifold temperature.

Possible Causes
-Stuck in-range engine intake manifold temperature sensor reading.
-High resistance in the engine intake manifold temperature sensor signal or return lines