SUPPORT GP- 3048470 - Caterpillar

Illustration 1 g01126547
The ECM monitors the status of the key switch, however, the ECM does not perform any diagnostics for the switch. If the voltage at ECM input contact J1-40 is less than 21 DCV, the ECM will not allow the burners to ignite. If the key switch is OFF and the voltage at the key switch ECM input is a constant 21 DCV, then the burners will attempt to ignite and will not be successful since the fuel pump will not be powered.Perform the following procedure when the key switch is suspected to be malfunctioning.Test Step 1. Check Key Switch On Input
Turn the key start switch to the ON position.
Disconnect the machine harness connector J1 from the ECM.
Measure the voltage between contacts J1-40 (wire P120-YL) and J1-2 (P200-BK).Expected Result:The voltage measurement should be greater than 21 DCV.Results:
OK - The voltage measurement is greater than 21 DCV.Repair: The key switch ECM input works properly with the key switch ON. Proceed to Step 2 in order to check the key switch in the OFF position
NOT OK - The voltage measurement is less than 21 DCV.Repair: The key switch input is not working properly. Proceed to Step 3.Test Step 2. Check Key Switch Off InputThe machine harness connector J1 remains disconnected from the ECM.
Turn the key start switch to the OFF position.
Measure the voltage between contacts J1-40 (wire P120-YL) and J1-2 (P200-BK).Expected Result:The voltage measurement should be less than 21 DCV.Results:
OK - The voltage measurement is less than 21 DCV.Repair: The key switch ECM input is correct. If the ECM does not attempt to ignite the burners when the machine is ON, ensure that the following conditions are met. The burner system switch is ON, the burner circuit breaker is OK and the burner mode switch is in AUTO mode. If all of these conditions are correct, check the burner temperature switch by performing the "Burner Temperature Switch" procedure in this section of the manual. Stop.
NOT OK - The voltage measurement is more than 21 DCV.Repair: The key switch input is not correct. Proceed to Step 5.Test Step 3. Check Screed Horns
Turn the key switch to the ON position.
Operate the screed horns.Expected Result:The screed horns operate correctly.Results:
OK - The screed horns do operate correctly.Repair: The key switch and the screed horn circuit breaker (CB12) are operating correctly. It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. Refer to the Electrical System Schematic for this machine and check all involved wiring harness connectors and wiring. Ensure that the ECM connector contacts are clean and in good condition. Ensure that all machine harness wiring is intact and in good condition. If the key switch input for the ECM does not operate correctly after this procedure has been performed, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace" in this manual. Stop.
NOT OK - The screed horns do not operate correctly.Repair: Either the screed horn circuit breaker CB12 is not operating correctly