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Cummins: Fault Code: 377 PID: S233 SPN: 1077 FMI: 7

The document describes a fault code indicating a fuel pump power relay is stuck on in a Cummins engine. It provides the fault code number, PID, SPN, and FMI identifying the issue. The description explains that the fault occurs if the ECM continues detecting messages from the fuel pump after the key is turned off. Troubleshooting steps include checking for shorts, stuck relays, and measuring voltages to diagnose whether the engine harness, fuel pump relay, or ECM is causing the relay to remain powered.

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Enrrique Lara
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1K views3 pages

Cummins: Fault Code: 377 PID: S233 SPN: 1077 FMI: 7

The document describes a fault code indicating a fuel pump power relay is stuck on in a Cummins engine. It provides the fault code number, PID, SPN, and FMI identifying the issue. The description explains that the fault occurs if the ECM continues detecting messages from the fuel pump after the key is turned off. Troubleshooting steps include checking for shorts, stuck relays, and measuring voltages to diagnose whether the engine harness, fuel pump relay, or ECM is causing the relay to remain powered.

Uploaded by

Enrrique Lara
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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FUEL PUMP POWER RELAY STUCK-ON

CUMMINS

FAULT CODE: 377


PID: S233
SPN: 1077
FMI: 7

Fuel Pump Circuit


DESCRIPTION
This circuit is internal to the ECM. If the key switch is turned off
and the ECM still detects messages being sent from the fuel pump,
the ECM will log this fault.
- Some older ISB engines use a different OEM interface connector
than illustrated.
- Fault Code 377 can be caused by a stuck VP44 relay. If voltage is
detected at pin 7 of the VP44 connector, with the key switch in the
OFF position, check for a faulty VP44 relay.
COMPONENT LOCATION
This circuit logic is internal to the ECM.

TROUBLESHOOTING STEPS
Step 1A) Turn key switch OFF and disconnect the engine harness connector from the ECM. Disconnect the
fuel pump relay connector from the engine harness. Inspect the engine harness, fuel pump, and ECM
connector pins for the following:
• Bent or broken pins
• Pushed back or expanded pins
• Corroded pins
• Moisture in or on the connector
• Missing or damaged seals
No damaged pins?

Yes - Go to 1B No - Repair or replace the damaged pins


Go to 3A

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Step 1B) Turn key switch to the OFF position and disconnect the engine harness from the ECM. Disconnect
the engine harness from the fuel pump. Check for a short circuit from pin to pin. Measure the resistance from
pin 43 to pins 16, 6, 11, 5, 38, 39, 40, 31, and 42.

More than 100k ohms?

Yes - Go to 1C No - Replace the engine harness


Go to 3A

Step 1C) Disconnect VP44 relay from the engine harness and connect ECM to the engine harness. Turn
key switch ON and check for a short circuit to an external voltage source in the VP44 voltage supply circuit.
Measure the voltage from pin A of the VP44 relay connector, harness side, to engine block ground.

Less than 1.0 VDC?

Yes - Go to 2A No - Replace the engine harness


Go to 3A

Step 2A) Turn key switch OFF and disconnect the fuel pump relay from the engine harness. Check for stuck
“ON” relay. Measure resistance between pin 30 and post 87 of the VP44 relay.

More than 100k ohms?

Yes - Go to 3A No - Replace the fuel pump relay


Go to 3A

Step 3A) Connect all components. Turn key switch ON and disable the fault code. Start the engine and let
idle for one minute. Verify that Fault Code 377 is inactive.

Fault Code 377 inactive?

Yes - Go to 3B No - Return to troubleshooting steps or contact local


Cummins Authorized Repair Location if all steps
have been completed and checked again
Go to 1A
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Step 3B) Connect all components. Turn key switch ON and clear the inactive fault codes using the
diagnostic tool.
All fault codes cleared?

Yes - Repair is complete No - Troubleshoot any remaining active fault codes


with appropriate troubleshooting steps.

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