Cummins ISM CM870 (2003-06) Fault Code: 2321 PID: P190 SPN: 190 FMI: 2/2 Engine speed/position sensor number 1 – engine speed/position glitch detect (crankshaft sensor).

The CM870 controls are able to function almost normally on a single speed sensor. In the event that there is a signal glitch on the engine speed sensor, the system controls transfer to the camshaft position sensor. After awhile, the camshaft position sensor will transfer controls back to the engine speed sensor. When the controls transfer from one sensor to the next, a few actuator pulses may be skipped. This transition between sensors may be seen as a glitch, dropout, or miss. Fault Code 2321 serves as a tool to identify the source of those glitches in the event that a customer has a complaint regarding glitches, dropouts, or misses.

This fault becomes inactive at each key ON or if the ECM does not detect a loss of the engine speed sensor signal for at least 20 minutes.

Possible causes:

1)Loose, damaged, or corroded ECM or sensor connection
2)Engine harness insulation damage
3)Pushed back or bent ECM, sensor, or harness pins.

Actions to take if fault is intermittent:

1)Look for intermittent engine harness connections in the primary engine speed sensor circuit.

Possible repairs:

1)Repair or replace the engine harness.