Understanding Diagnostic Trouble Codes (DTCs) for Bad Fuel Pumps

A car can throw a diagnostic trouble code (DTC) when there is a problem with the fuel pump, but several factors determine if a code is generated. Whether a bad fuel pump triggers a DTC depends on the vehicle's onboard diagnostic system and the nature of the failure. This article explores key points, symptoms, and how to diagnose such issues.

Fuel Pump Circuit Issues

If there is an electrical issue with the fuel pump, such as a short circuit or an open circuit, the engine control module (ECM) can detect this and generate a code related to the fuel pump circuit. This can be a result of inadequate electrical supply to the fuel pump, leading to malfunction or even a complete failure.

Fuel Pressure Problems

A fuel pump that is not delivering the correct pressure can trigger a code if the pressure falls outside of specified parameters. Modern vehicles often have fuel pressure sensors that monitor the fuel system and can generate a diagnostic code if the pressure is either too high or too low. These sensors are particularly important in vehicles with sophisticated fuel delivery systems.

Common Symptoms of a Failing Fuel Pump

Common symptoms of a failing fuel pump include difficulty starting, engine misfires, a decrease in power, or stalling. If these symptoms are present, it is likely that a diagnostic code may be generated. For example, a lean engine condition due to a failing fuel pump can eventually trigger a code indicating a fuel system problem.

Using a Scan Tool to Diagnose the Issue

To determine if a diagnostic code has been thrown, a diagnostic scan tool can be used to read the trouble codes stored in the vehicle's Electronic Control Module (ECM). These tools can provide valuable information about the condition of the fuel pump and other components in the fuel system.

Special Considerations for High-End Vehicles

High-end vehicles, such as Mercedes or BMWs, often have fuel pressure sensors that can report fuel pressure via a diagnostic scan tool. However, these systems typically require a high-end scan tool to display the pressure readings accurately. If the fuel pressure is low, it may trigger a diagnostic code, but this is not always the case.

Diagnosing the Fuel System Issue

A bad fuel pump can cause a lean condition in the engine, leading to the generation of diagnostic codes. If the failure is gradual and not causing immediate issues such as a check engine light, it is still important to check the fuel rail pressure. To do this, install a fuel pressure gauge on the rail and turn the ignition key to run. The pump should be functional and run for a few seconds, allowing for the pressure to build up in the fuel rail.

Here are some troubleshooting steps to identify the cause:

Check the fuse: Ensure that the fuse has power. Test for power at the fuel pump connection at the tank: Use a test light when the key is turned to run. If there is no power, the issue could be a faulty fuel pump relay or a break in the wire going to the pump. Location-specific issues: For an F150, check under the truck right under the driver for any broken wires.

If power is present at the connection under the tank, the fuel pump itself may be faulty (NFG - Not For Garbage).

Understanding the diagnostic trouble codes related to a bad fuel pump can help you identify and resolve underlying issues effectively. Regular maintenance and monitoring of the fuel system ensure optimal performance and longevity of your vehicle.