Cummins ISL CM850 (2003-06) Fault Code: 1639 PID: SID 51 SPN: 703 FMI: 11 Auxiliary Equipment Sensor Input Number 3 (OEM Switch) – Root Cause Not Known.

Cummins ISL CM850 (2003-06) Fault Code: 1639 PID: SID 51 SPN: 703 FMI: 11 Auxiliary Equipment Sensor Input Number 3 (OEM Switch) – Root Cause Not Known.

This fault code is activated when the maximum inlet temperature or inlet pressure of a third party after-treatment system has exceeded the maximum allowable limits. A power derate may or may not be associated with this fault code.

Possible repairs:

1)Replace the ECM.
2)Repalce the OEM harness.