CM850 Electronic Control System – 019-327   Engine Protection Override Switch

General Information

TOC

The engine protection override switch is an original equipment manufacturer (OEM) installed switch that allows a driver to abort a pending engine protection shutdown. The switch is
only active when it is properly wired by the OEM and the engine protection shutdown override feature is enabled in the calibration. If the switch is
not preventing a shutdown from occurring, check the feature with the electronic service tool to see if it is enabled in the calibration.

 
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Resistance Check

TOC

If INSITE™ electronic service tool is available, monitor the engine protection override switch for proper operation. If
not, follow the troubleshooting procedures in this section.

Locate the engine protection override switch. Label the wires with the location on the switch or the wire number. Remove the electrical connectors from the switch. Adjust the multimeter to measure resistance. Touch one multimeter probe to one of the terminals on the switch. Touch the other multimeter probe to the other terminal of the switch.

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Place the switch in the non-override (released) position and measure the resistance. The multimeter
must show an open circuit (100k ohms or more). If the circuit is
not open, the switch is defective. Refer to the original equipment manufacturer (OEM) troubleshooting and repair manual for replacement procedures.

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Place the switch in the override (pressed) position and measure the resistance. The multimeter
must show a closed circuit (10 ohms or less). If the circuit is
not closed, the switch is defective. Refer to the OEM troubleshooting and repair manual for replacement procedures. If the resistance value is correct, the switch
must still be checked for a short circuit to ground.

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Check for Short Circuit to Ground

TOC

Touch one of the multimeter probes to one of the switch terminals. Touch the other probe to chassis ground. Move the switch to the non-override (released) position and measure the resistance. The multimeter
must show an open circuit (100k ohms or more).

If the circuit is
not open, the switch has failed. Refer to the OEM troubleshooting and repair manual for replacement procedures.

If the switch passes all of the previous checks, the circuit
must be checked for an open circuit, a short circuit to ground, a short circuit from pin-to-pin, and a short circuit to an external voltage source.

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Last Modified:  30-May-2008