Cummins ISB CM850 (2003-06) Fault Code: 2322 PID: SID 64 SPN: 723 FMI: 2 Backup Engine Speed/Position Sensor Number 2 – Data Erratic, Intermittent, or Incorrect. Camshaft engine speed sensor intermittent synchronization.

During engine operation, the ECM monitors the secondary speed sensor (camshaft speed sensor) signal. Fault Code 778 will become active and light the yellow lamp (marine does not use lamps) if the signal from the secondary speed sensor is not present or degraded for more than three continuous seconds. If over a period of time, the ECM detects several incidents of a loss of the secondary speed sensor signal but the signal loss is short in duration, this fault code will become active. Since the secondary engine speed signal is not used for normal engine operation, a vehicle operator should not notice any symptoms related to this problem.

This fault code becomes active whenever the ECM detects a persistent loss of the secondary engine speed sensor signal over a short period of time.

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

Possible causes:

1)Intermittent loss of primary speed sensor signal. The most likely cause is an intermittent open or short circuit as can be experienced with speed sensor connector problems
2)Sensor air gap that is marginally too small or too large, or target wheel exhibits excessive runout.

Actions to take if this fault is intermittent:

1)Look for intermittent engine harness connections in the secondary engine speed sensor circuit
2)Look for loose connections at the ECM connector where the pins can not be locked into the socket
3)Look for places where the engine harness has worn into a nearby component causing an intermittent short circuit
4)Look for pin wear at the speed sensor
5)Inspect the target wheel for damage.

The sensor return configuration for Euro 4 ISB engines has been changed for automotive wiring harnesses manufactured from February 2012 onward. The new style wiring harnesses can be be identified using the method below:

1)Disconnect the ECM connector
2)Disconnect the camshaft position sensor
3)Disconnect the intake manifold pressure/temperature sensor
4)Check for continuity between the intake manifold pressure/temperature sensor RETURN pin and the camshaft position sensor RETURN pin
5)Check for continuity between ECM pin 47 and the camshaft position sensor RETURN pin
6)Use the table below to determine which harness is fitted to the engine.

NOTE: QSB engines, all C series engines, and all L series engines are not affected by this change.

Possible repairs:

1)Replace the Engine harness.
2)Replace or shim the sensor if air gap is out of specification. If the target runout is excessive, replace the target.