Cummins ISX CM870 (2003-06) Fault Code: 9121 PID: S146 SPN: 2791 FMI: 0/15 EGR Valve Actuator Over Temperature (Calculated) – Data Above Normal Range – least severe level.

The ECM calculates the temperature of the EGR valve motor. If the ECM detects excessive temperatures for a calibrated period of time this fault is recorded and the valve is commanded closed. This action is for protection of the valve only; this fault code is not indicative of any component failure. Once the ECM detects normal EGR valve temperatures, the fault code will go inactive and the EGR valve operation will resume.

NOTE: During this event, there will be no noticeable symptoms. This troubleshooting tree should not be considered if there is a performance complaint.

A combination of frequent valve movement and elevated coolant temperatures can lead to this fault code.