HARNESS AS 2420489 - Caterpillar

Disconnect the fuel pump.
Turn the keyswitch to the ON position.
Proceed to the "Diagnostic Overrides" screen on Cat ET.
Activate the relay for the fuel pump.Note: The diagnostic override will only activate the relay for 120 seconds.
Use signal reading probes to measure the voltage across terminal 2 (Ground) and terminal 5 (Fuel Pump Power) of the relay.Expected Result:The supply voltage is greater than 22.0 VDC.Results:
OK - The ECM is properly controlling the relay for the fuel pump, but the fuel pump is not working.Repair: Replace the fuel pump.Verify that the repair eliminates the problem.STOP
Not OK - The fuel pump is not receiving the correct signal. Proceed to Test Step 6.Test Step 6. Check the Resistance of the Relay
Illustration 5 g01116874
Relay Terminals
Turn the keyswitch to the OFF/RESET position.
Unplug the relay for the fuel pump.
Measure the resistance between terminal 1 (Fuel Pump Relay (Signal)) and terminal 2 (Ground) of the relay.Expected Result:The resistance is between 250 Ohms and 500 Ohms.Results:
OK - Proceed to Test Step 7.
Not OK - The relay is faulty.Repair: Replace the relay.Verify that the repair eliminates the problem.STOPTest Step 7. Check the Signal Voltage to the Relay
Illustration 6 g01116878
Relay Terminals
Unplug the relay for the fuel pump.
Turn the keyswitch to the ON position.
Proceed to the "Diagnostic Overrides" screen on Cat ET.
Activate the system for the fuel pump.Note: The diagnostic override will only activate the relay for 120 seconds.
Measure the voltage between terminal 2 (Ground) and terminal 1 (Fuel Pump Relay (Signal)) of the plug for the relay.Expected Result:The voltage is 24.0 8.0 VDC.Results:
OK - The relay is receiving the signal from the ECM. Proceed to Test Step 8.
Not OK - The relay is not receiving the signal from the ECM. Proceed to Test Step 10.Test Step 8. Check the Output Voltage of the Relay
Illustration 7 g01116872
Relay (Wire Side) (1) +BATT (2) Ground (3) Fuel pump power (4) Fuel pump relay (signal)
Ensure that all connectors are connected to the wiring harness.
Turn the keyswitch to the ON position.
Proceed to the "Diagnostic Overrides" screen on Cat ET.
Activate the system for the fuel pump.Note: The diagnostic override will only activate the relay for 120 seconds.
Use signal reading probes to measure the voltage across terminal 2 (Ground) and terminal 5 (Fuel Pump Power) of the relay.Expected Result:The voltage is 24.0 8.0 VDC.Results:
OK - There is a problem in the wiring between the relay and the fuel pump.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOP
Not OK - The relay is not sending power to the fuel pump. Proceed to Test Step 9.Test Step 9. Check the Power Supply to the Relay
Illustration 8 g01116878
Relay Terminals
Unplug the fuel pump.
Measure the voltage between terminal 3 (+Battery) of the connector for the relay and terminal 2 (Ground).Expected Result:The voltage is 24.0 8.0 VDC.Results:
OK - The relay is faulty.Repair: Replace the relay.Verify that the repair eliminates the problem.STOP
Not OK - There is a problem in the wiring between the relay and the +Battery terminal.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 10. Check for Shorts in the