Cummins ISB4.5 CM2150 Fault Code: 693 PID: 351 SPN: 1172 FMI: 2 Turbocharger 1 Compressor Intake Temperature – Data Erratic, Intermittent, or Incorrect.

Posted by PerDiezel Solutions on January 20, 2026

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 volts 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
Some engines use a combination ambient air temperature/pressure sensor located in the OEM intake air plumbing rather than a turbocharger compressor intake temperature sensor. Refer to the engine wiring diagram to determine which sensor this application uses.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes
The ECM detects that the compressor intake temperature reading is too high or too low for the engine operating conditions.

Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails. A default value for the compressor intake temperature reading is used.

Conditions for Clearing the Fault Code
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

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

Cummins ISB4.5 CM2150 Fault Code: 692 PID: 351 SPN: 1172 FMI: 4 Turbocharger 1 Compressor Intake Temperature Circuit – Voltage below normal, or shorted to low source.

Cummins ISB4.5 CM2150 Fault Code: 691 PID: 351 SPN: 1172 FMI: 3 Turbocharger 1 Compressor Intake Temperature Sensor Circuit – Voltage Above Normal or Shorted to High Source.

Cummins ISB4.5 CM2150 Fault Code: 689 PID: 190 SPN: 190 FMI: 2 Engine Crankshaft Speed/Position – Data Erratic, Intermittent, or Incorrect.

Cummins ISB4.5 CM2150 Fault Code: 688 PID: SPN: 98 FMI: 0 Engine Oil Level – Data Valid but Above Normal Operating Range – Most Severe Level.

Cummins ISB4.5 CM2150 Fault Code: 687 PID: 103 SPN: 103 FMI: 1 Turbocharger 1 Speed – Data Valid but Below Normal Operating Range – Moderately Severe Level.

Cummins ISB4.5 CM2150 Fault Code: 686 PID: 103 SPN: 103 FMI: 2 Turbocharger 1 Speed – Data Erratic, Intermittent, or Incorrect.

WARNING!