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SPN 723 - FMI 7 (Fault Code 731)

SPN723 FMI7 (Engine Speed/Position Camshaft and Crankshaft Misalignment - Mechanical System Not Responding Properly or Out of Adjustment)
Fault Code 731
ISB, ISC, and ISL with CM2150 - Engine Magnetic Speed/Position Sensor Circuit

CODES:
Fault Code: 731
PID(P), SID(S): S064
SPN: 723
FMI: 7/7
Lamp: AMBER
SRT:

REASON: Engine Speed/Position Camshaft and Crankshaft Misalignment - Mechanical System Not
Responding Properly or Out of Adjustment. Engine position signal from the engine speed sensor and
camshaft position sensor do not match.

EFFECT: Engine will run derated. Hard start and rough idle possible.

Circuit Description:
The crankshaft position and camshaft position sensors are hall effect type sensors. The electronic control module (ECM) provides a 5-VDC supply to the position sensor and a return circuit. As the teeth on the crankshaft speed ring or the lobes on the camshaft gear pass the position sensor, a signal is generated on the position sensor signal circuit. The ECM interprets this signal and converts it to an engine speed. A missing tooth on the crankshaft gear is used to determine the position of the engine by the ECM.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes:
The ECM detects that the crankshaft position 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 light immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk:
Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.

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.

This fault code is logged when there is a mechanical misalignment between the crankshaft engine position sensor and the camshaft engine position sensor.

Possible causes for this fault code include:
• Engine speed sensor rings that are loose or not aligned correctly
• Mechanical misalignment.


Read More:
SPN 1172 - FMI 4 (Fault Code 692)
SPN 1172 - FMI 3 (Fault Code 691)








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