Cummins ISB CM850 (2003-06) Fault Code: 2559 PID: SPN: 1845 FMI: 4 Transmission ECU to ECM Communication Lost – Abnormal Update Rate. No communication or an invalid data transfer rate has been detected between the ECM and the transmission ECU.

Posted by PerDiezel Solutions on January 18, 2026

When this fault code is active, some multiplexed devices may not function as desired.

Possible causes:

1)When the ECM is set up properly (components enabled and OEM VECU source addressed correctly) to receive information from an OEM VECU, but the OEM VECU is actually transmitting a message that says that component is not available for multiplexing. This can be caused when a multiplexed component is enabled in the Cummins? ECM, but the OEM VECU source address of the VECU transmitting the component message is incorrect in the Cummins? ECM, or the OEM VECU is not set up to transmit the multiplexed component message.
2)This fault can also be caused by a malfunctioning data link connection between the OEM VECU and Cummins? ECM, a malfunctioning connection between the component and the OEM VECU, a malfunctioning OEM VECU, or a malfunctioning Cummins? ECM. It may be necessary to contact the OEM for the proper multiplexing configuration.

Possible repairs:

1)Repair or replace the OEM harness.
2)If necessary, calibrate the ECM.

Cummins ISB CM850 (2003-06) Fault Code: 2558 PID: SID 57 SPN: 697 FMI: 4 Auxiliary PWM Driver #1 – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the analog torque circuit.

Cummins ISB CM850 (2003-06) Fault Code: 2557 PID: SID 57 SPN: 697 FMI: 3 Auxiliary PWM Driver #1 – Voltage Above Normal or Shorted to High Source. High signal voltage detected at the analog torque circuit.

Cummins ISB CM850 (2003-06) Fault Code: 2556 PID: SID 70 SPN: 729 FMI: 4 Intake Air Heater #1 Circuit – Voltage Below Normal or Shorted to Low Source. Low voltage detected at the intake air heater signal circuit.

Cummins ISB CM850 (2003-06) Fault Code: 2555 PID: SID 70 SPN: 729 FMI: 3 Intake Air Heater #1 Circuit – Voltage Above Normal or Shorted to High Source. High voltage detected at the intake air heater signal circuit.

Cummins ISB CM850 (2003-06) Fault Code: 2554 PID: 95 SPN: 1209 FMI: 2 Exhaust pressure sensor circuit – data erratic, intermittent, or incorrect. An error in the exhaust pressure sensor signal was detected by the ECM.

Cummins ISB CM850 (2003-06) Fault Code: 2448 PID: SPN: 111 FMI: 17 Coolant Level – Data Valid But Below Normal Operational Range – Least Severe Level. Low engine coolant level detected.

WARNING!