Mechanical Gas Fuel System G5.9, G8.3, G855 – Master Repair Manual 019-042   Engine Speed Sensor (ESS)

General Information

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NOTE: Shown throughout this procedure are the QSV81 and QSV91 graphics. Although this is a different engine, the procedure remains the same. Refer to the Engine Diagrams in Procedure 100-002 for the component location.

The engine speed sensor sends a speed signal to the CM558 or electronic governor.

The second sensor sends a speed signal to the ignition module.

NOTE: If an error occurs, the fault code will identify which engine speed sensor requires testing or replacement.

 
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Remove

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Disconnect the engine speed sensor connectors from the engine harness.

Loosen the locknut.

Remove the engine speed sensor from the flywheel housing.

This applies to both sensors.

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Inspect for Reuse

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Inspect the engine speed sensor for debris, cracked potting, chipped potting, extruded potting, and damage from contact with the flywheel.

If there is debris on the engine speed sensor, clean the sensor.

If the sensor potting is chipped, cracked, or extruded, or if the sensor has been damaged by contact with the flywheel, replace the sensor with a new one.

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Install

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When installing the engine speed sensor, make sure a flywheel tooth is aligned with the hole in the flywheel housing.

Install the sensor into the hole until it touches the flywheel.

NOTE: If the sensor does not turn in with finger pressure, check the flywheel housing hole threads and sensor threads for damage.

Turn the engine speed sensor counterclockwise 1/2 to 3/4
(3 to 4 flats of the locknut) of a turn.

NOTE: For the KTA38GC, turn the engine speed sensor counterclockwise 2 turns.

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Tighten the locknut against the flywheel housing.

KTA38GC 27 n.m [20 ft-lb]
All Other Engines 47 n.m [35 ft-lb]

NOTE: Overtightening the locknut can damage the sensor.

Connect the sensor to the sensor harness. Push the connectors together until they lock.

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Resistance Check

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Disconnect the engine speed sensor connectors from the engine harness.

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Measure the resistance from pin to pin for each coil. The multimeter must measure between 700 and 2000 ohms. If both resistance values are within specifications, the sensor must still be checked for a short to ground.

If any of the preceding checks fail, replace the engine speed sensor.

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Check for Short Circuit to Ground

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Measure the resistance from both pins on each connector to the engine block. The multimeter must show an open circuit (100k ohms or more).

If either connector fails the test, replace the engine speed sensor.

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Check for Short Circuit from Pin to Pin

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Measure the resistance from pin to pin for each coil. The multimeter must show an open circuit (100k ohms or more).

If either connector fails the test, replace the engine speed sensor.

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Last Modified:  07-Jul-2006