SPN 723 - FMI 7 (Fault Code 731)

Engine Speed/Position Camshaft and Crankshaft Misalignment - Mechanical System Not Responding or Out of Adjustment

Engine Speed and Position Sensors

Fault Code: 731
PID(P), SID(S): S64
SPN: 723
FMI: 7/7
Lamp: Amber

REASON: Engine position signal from the crankshaft position sensor and camshaft position sensor do not match.

EFFECT: Engine power derate. Engine may run rough, may stop running, may not start, or may be difficult to start.

Circuit Description:
The engine speed sensor and camshaft position sensor provide an engine speed and position signal to the engine control module (ECM) through the engine harness.

Component Location:
The crankshaft position and camshaft position sensor location varies, depending on engine model.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the engine speed sensor does not match the camshaft position signal input to the ECM.

Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
• To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
• The fault code status displayed by the recommended Cummins® electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
• The “Reset All Faults” command in the recommended Cummins® electronic service tool or equivalent can be used to clear active and inactive faults.

Shop Talk:
The ECM monitors the position of the missing tooth on the crankshaft speed sensor target and the camshaft speed sensor target. If the two positions do not match, the ECM then determines that there is a mechanical misalignment between the two sensors.

-Possible causes of this fault code include:
Engine speed sensor rings that are loose or not aligned correctly.

-Mechanical misalignment.
• Loose, missing, or corroded grounds
-Damage to the sensor target teeth or tone wheel.
• Loose tone wheel
-Base engine timing is incorrect.
• Gear train wear.
• Misoriented engine speed or camshaft position sensor
-Electronic vehicle accessories which emit excessive electromagnetic interference.

Read More:
SPN 157 - FMI 7 (Fault Code 755)
SPN 723 - FMI 10 (Fault Code 753)


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