RING 3J8466 - Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the fuel pump relay. Also, use this procedure if one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
CDL Code and Description Conditions which Generate the Code System Response
1627-5
Fuel Pump Relay current below normal The Electronic Control Module (ECM) detects an open circuit at the fuel pump relay for 60 seconds.
The ECM detects a short to battery voltage for the fuel pump relay for 60 seconds.
The ECM can only detect this condition when the output driver is not activated. The code is logged.
1627-6
Fuel Pump Relay current above normal The ECM detects a short circuit for the fuel pump relay.
The ECM can only detect this condition when the output driver is activated. During the following scenarios ECM energizes the fuel pump relay. The fuel pump relay controls battery power to the fuel priming pump.ECM Activation of the Fuel Priming PumpThis strategy improves the capability of the fuel system at low engine speeds.The ECM will automatically activate the fuel priming pump while the engine state is CRANKING, RUNNING, or POSTRUN. The ECM deactivates the fuel pump when the engine speed is greater than 200 rpm.Manual Override of the Fuel Priming PumpUse the "Fuel Priming Pump Command Override" in Cat® Electronic Technician (ET) to diagnose a problem with the electric fuel priming pump. A "Fuel Priming Pump Command" parameter is also available in Cat ET that can be used to view the status of the ECM output.When the override is activated, the ECM powers the electric fuel priming pump. The ECM will command the FCV throttle position to 25 percent. Opening the FCV throttle provides a path for air to escape from the low-pressure fuel system. To use this feature, the ECM and the keyswitch relay must be powered. Also, the engine speed must be 0 rpm.
Illustration 1 g02783247
Schematic for the electric fuel priming pump (control assembly input connectors) if equipped with an A4 ECM
Illustration 2 g06320834
Schematic for the electric fuel priming pump (control assembly input connectors) if equipped with an A5 ECM
Illustration 3 g02783249
Schematic for the electric fuel priming pump (control assembly output connector) if equipped with an A4 ECM
Illustration 4 g06328492
Schematic for the electric fuel priming pump (control assembly output connector) if equipped with an A5 ECM
Table 2
Troubleshooting Test Steps Values Results
1. Inspect the Electrical Connectors and the Wiring
A. Turn the battery disconnect switch to the OFF position.
B. Thoroughly inspect the electrical connectors and breakers. Reset the breaker, if necessary. Refer to Troubleshooting, "Electrical Connectors - Inspect"
C. Check the torque of the allen head screws for each of the ECM connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
D. Check the harness and the wiring for abrasion and for pinch points from the connectors for the fuel priming pump to the ECM.
Connectors
Results: The connectors and the wiring appear to be OK.
Proceed to Test Step 2
Results: The connectors and/or the wiring are not OK.
Repair The connectors and/or the wiring. Replace parts, if