EDGE 4T3024 - Caterpillar

Use this procedure to troubleshoot a problem with the fuel pump relay. Also, use this procedure if one of the following diagnostic codes is active or easily repeated.
Table 1
J1939 Codes and Description CDL Codes and Description Comments
931-5
Engine Fuel Supply Pump Actuator : Current Below Normal 1627-5
Fuel Pump Relay : Current Below Normal The engine 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.
The ECM can only detect this condition when the output driver is not activated.
931-6
Engine Fuel Supply Pump Actuator : Current Above Normal 1627-6
Fuel Pump Relay : Current Above Normal The engine ECM detects a short circuit for the fuel pump relay.
The ECM can only detect this condition when the output driver is activated. The Electronic Control Module (ECM) is able to energize the fuel pump relay. The fuel pump relay controls battery power to the fuel priming pump. The circuit that is for battery power uses a 10 amp fuse for circuit protection. This circuit also provides battery power to the power module that is for the fuel control valve controller.Manually Priming the Fuel SystemA manual switch can be used to prime the fuel system. This switch is used after maintenance has been performed on the fuel system allowing air to be purged from the system without opening up fuel lines. The switch is located near the high-pressure fuel pump on the right side of the engine.When the switch is activated, the ECM powers the electric fuel priming pump. The ECM will command the throttle position for the fuel control valve to 25 percent providing a path for the air. To use this feature, the keyswitch must be in the ON position. Also, the engine speed must be 0 rpm.The switch for the fuel priming pump is a normally open switch.
Illustration 1 g06242700
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Connect Cat® Electronic Technician (ET) to the service tool connector.
B. Determine if a code is active or logged.
Codes
Result: A -5 code is active or logged.
Proceed to Test Step 2.
Result: A -6 code is active or logged.
Proceed to Test Step 3.
2. Check the Wiring for an Open Circuit
A. Verify that the harness connector is free of debris, free of corrosion, and securely connected.
B. Disconnect the solenoid from the engine harness.
C. Connect a jumper wire between the terminals of the wiring harness connector for the affected coil. The coil is replaced with a short circuit.
D. Use Cat ET to perform the following override:
- "Fuel Pump Relay Command Override"
Open Circuit
Result: A -5 code became active.
The Electronic Control Module (ECM) did not detect the jumper wire. There is an open circuit in the wiring between the coil and the ECM connector. There may be a problem with a connector.
Repair: Repair or replace the wiring harness.
Verify that the repair eliminated the problem.
Result: A -6 code became active. The ECM detected the jumper wire. There is a problem with the solenoid. Clear the