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.

Circuit Description
The turbocharger speed sensor is a variable reluctance speed sensor. It consists of a coil of wire and an iron core. The target on the turbocharger shaft is a ground flat in the center of the shaft. As the flat on the turbocharger shaft spins past the speed sensor, a signal is generated. The electronic control module (ECM) interprets this signal and converts it to a turbocharger speed reading.

Component Location
The turbocharger speed sensor is mounted in the center housing of the turbocharger.

Conditions for Running the Diagnostics
This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes
The ECM detects that the turbocharger speed is detected to be less than 600 rpm for more than 1 second when the engine speed is greater than 1200 rpm.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
-The ECM will estimate turbocharger speed.

Conditions for Clearing the Fault Code
The ECM will turn off the amber CHECK ENGINE light immediately after a valid speed signal from the turbocharger speed sensor returns, and the diagnostic runs and passes.

Possible Causes
-Damaged turbocharger speed sensor
-Damaged engine harness
-Damaged ECM.

If the fault occurs intermittently, look for causes of intermittent open or short circuits in the turbocharger speed sensor circuit (including the speed sensor pigtail connector).