Cummins ISB CM850 (2003-06) Fault Code: 687 (ISB) PID: 103 SPN: 103 FMI: 18 Turbocharger number 1 speed low – warning level. Low turbocharger speed detected by the ECM.

Cummins ISB CM850 (2003-06) Fault Code: 687 (ISB) PID: 103 SPN: 103 FMI: 18 Turbocharger number 1 speed low – warning level. Low turbocharger speed detected by the ECM.

This fault will become active if the engine is running and the ECM detects boost pressure and engine speed but no turbocharger speed signal.

Possible causes:

1)Turbocharger speed sensor failure
2)Engine harness failure
3)ECM failure.

This fault becomes inactive at key-on or any time the speed signal from the turbocharger speed sensor returns. If the fault occurs intermittently, Fault Code 2345 can also be in the ECM memory. Look for causes of intermittent open circuit or short circuits in the turbocharger speed sensor circuit (including the speed sensor pigtail connector).

Possible repairs:

1)Repair or replace the engine harness.
2)Replace the ECM.
3)Replace the turbocharger speed sensor.