Cummins ISB CM850 (2003-06) Fault Code: 595 (ISC) PID: 103 SPN: 103 FMI: 0 Turbocharger Number 1 Speed High – Data Valid but Above Normal Operational Range – Moderately Severe Level. High turbocharger speed has been detected.

Posted by PerDiezel Solutions on January 18, 2026

This fault can come active any time the key is on and the electronic control module (ECM) detects turbocharger speed greater than a calibration limit.

This fault can be caused by failures in the following components:

1)Turbocharger speed sensor
2)Engine harness
3)ECM power supply or grounds
4)Electronic vehicle accessories which emit excessive electromagnetic interference.

This fault becomes inactive any time the ECM detects a valid turbocharger speed.

If the fault occurs intermittently:

1)Look for causes of intermittent open circuit or short circuits in the turbocharger speed sensor circuit (including the speed sensor pigtail connector).
2)Look for sources of electronic noise such as poorly installed vehicle electronic components.
3)Ensure that vehicle chassis grounds are in good condition.
4)Ensure that the ECM power supply and ground circuits are in good condition and that this power supply is not shared with other vehicle electronics.

Possible repairs:

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

Cummins ISB CM850 (2003-06) Fault Code: 585 PID: SID 39 SPN: 677 FMI: 4 Starter Relay Circuit – Voltage Below Normal or Shorted to Low Source. Low voltage detected at starter lockout circuit.

Cummins ISB CM850 (2003-06) Fault Code: 584 PID: SID 39 SPN: 677 FMI: 3 Starter Relay Circuit – Voltage Above Normal or Shorted to High Source. Open circuit or high voltage detected at starter lockout circuit.

Cummins ISB CM850 (2003-06) Fault Code: 559 (ISC) PID: 94 SPN: 94 FMI: 0 Injector Metering Rail 1 Pressure – Data Valid but Below Normal Operational Range – Moderately Severe Level. The ECM has detected that fuel pressure is lower than commanded pressure.

Cummins ISB CM850 (2003-06) Fault Code: 559 (ISB) PID: 157 SPN: 157 FMI: 1 Fuel Pump Delivery Pressure Low – Data Valid but Below Normal Operational Range – Moderately Severe Level. The ECM has detected that fuel pressure is lower than commanded pressure.

Cummins ISB CM850 (2003-06) Fault Code: 554 PID: 157 SPN: 157 FMI: 2 Injector Metering Rail 1 Pressure – Data Erratic, Intermittent, or Incorrect. the ECM has detected that the fuel pressure signal is not changing.

Cummins ISB CM850 (2003-06) Fault Code: 553 PID: 157 SPN: 157 FMI: 0 Injector Metering Rail 1 Pressure – Data Valid but Above Normal Operational Range – Moderately Severe Level. The ECM has detected that fuel pressure is higher than commanded pressure.

WARNING!