DISTRIBUTION AR 3405671 - Caterpillar

Illustration 1 g01317674
Connections of the secondary steer test switch and hydraulic pilot supply filter bypass switch The secondary steer test switch and the hydraulic pilot filter bypass switch will supply one switch to ground input to the Implement ECM. The ECM does not monitor switch circuits that have one input for diagnostics.During normal operation, the internal "pull up voltage" of the ECM will hold the input circuit of the switch "high" until the circuit is grounded through the switch contacts. The ECM detects the low signal in the circuit and the ECM determines that the switch contacts are closed.The following conditions could occur if the switch circuit is open or the switch has failed in the open state:
The ECM will not detect the closed status of the switch contacts.
The ECM will not activate the function which is assigned to the switch.If the switch contacts are failed in the closed state or the circuit is shorted to ground, the ECM will not detect the high signal in the circuit in order to indicate that the contacts are open. When this occurs, the ECM will activate the function for the switch which is assigned.Some conditions that can cause an input circuit of the switch to fail are listed below:
The switch has failed.
The common ground circuit for the switch is an open or the circuit has a poor connection.
The input circuit of the switch is an open or the circuit has a poor connection in the machine harness.
The input circuit of the switch is shorted to another ground source in the machine harness.
The ECM has failed. This is not likely.When a switch circuit is suspected of improper operation, perform the following troubleshooting procedure.Test Step 1. CHECK THE SWITCH
Turn the disconnect switch to the OFF position.
Turn the key start switch to the OFF position.
At the two contacts for the suspect switch, use a multimeter to perform the following:
Measure the resistance between the switch contacts.
Measure the resistance with the switch in the OPEN position.
Measure the resistance with the switch in the CLOSED position.
Measure the resistance several times.Expected Result:When the switch contacts are open, the resistance measurement is greater than 5000 ohms. When the switch contacts are closed, the resistance measurement is