Cummins ISB4.5 CM2150 Fault Code: 4948 PID: SPN: 6874 FMI: 3 Performance Bias Selection Switch Circuit – Voltage Above Normal or Shorted to High Source.

Posted by PerDiezel Solutions on January 20, 2026

Circuit Description
The User Adjustable Fuel Economy feature provides three different engine operation modes through a three positon switch. The driver can balance fuel economy and vehicle power performance by running on different engine operation modes.

Component Location
The performance bias selection switch is installed in the dashboard or any other place in the cab that the driver can easily get access.

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

Conditions for Setting the Fault Codes
The engine control module (ECM) detected the performance bias selection switch signal voltage was out of range high.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code
-To validate the repair, perform a key cycle, start the engine, and let it idle for 1 minute.
-The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
-The “Reset All Faults” command in INSITE™ electronic service tool can be used to clear active and inactive faults.

Shop Talk
If the fault code is intermittent, inspect the ECM connector, wiring harness, and harness connectors for loose pins and bad connections. Look closely for loose wire connections that can cause an intermittent short to ground or open circuit in the wiring harness or connectors. It may help to wiggle the harness and harness connections and watch for fault code state changes.

Possible Causes
-An open circuit in the engine harness
-A malfunctioning performance bias selection switch.

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Cummins ISB4.5 CM2150 Fault Code: 4737 PID: SPN: 3031 FMI: 11 Aftertreatment 1 Diesel Exhaust Fluid Tank Temperature – Root Cause Not Known.

Cummins ISB4.5 CM2150 Fault Code: 4732 PID: SPN: 1761 FMI: 13 Aftertreatment Diesel Exhaust Fluid Tank Level Sensor – Out of Calibration.

Cummins ISB4.5 CM2150 Fault Code: 4731 PID: SPN: 3031 FMI: 13 Aftertreatment Diesel Exhaust Fluid Tank Temperature Sensor – Out of Calibration.

Cummins ISB4.5 CM2150 Fault Code: 4642 PID: SPN: 97 FMI: 0 Water-in-Fuel Indicator – Data Valid But Above Normal Operating Rage – Moderately Sever Level.

WARNING!