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Engine-Codes – Mercury – P0231 Mercury

P0231 Mercury Code - Fuel Pump Secondary Circuit Low

Quick Answer

The P0231 diagnostic trouble code (DTC) for Mercury vehicles indicates a problem with the fuel pump secondary circuit being low. Common causes include Faulty fuel pump relay, Malfunctioning fuel pump, Wiring or connection issues in the fuel pump circuit. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0231 Mercury indicates Fuel Pump Secondary Circuit Low.
Common causes
Common causes include Faulty fuel pump relay, Malfunctioning fuel pump, Wiring or connection issues in the fuel pump circuit.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 12, 2024
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Code P0231 Mercury Description

The P0231 diagnostic trouble code (DTC) for Mercury vehicles indicates a problem with the fuel pump secondary circuit being low. This code is typically triggered when the powertrain control module (PCM) detects that the voltage in the fuel pump secondary circuit is below the specified range. The fuel pump secondary circuit is responsible for providing power to the fuel pump relay, which in turn controls the fuel pump's operation. When this circuit is not functioning properly, it can lead to a variety of issues that can affect the vehicle's performance and fuel delivery system.

OBDII Code P0231 Mercury - Fuel Pump Secondary Circuit Low
P0231 Mercury Code - Fuel Pump Secondary Circuit Low

Common Causes of P0231 Mercury

  1. Faulty fuel pump relay
  2. Malfunctioning fuel pump
  3. Wiring or connection issues in the fuel pump circuit
  4. PCM failure
  5. Corrosion or damage to electrical connections

Symptoms of P0231 Mercury

  1. Engine misfires or hesitation during acceleration
  2. Difficulty starting the engine
  3. Check engine light illuminated on the dashboard
  4. Reduced fuel efficiency
  5. Engine stalling or shutting off unexpectedly

How to Fix P0231 Mercury

  1. Begin by conducting a thorough inspection of the fuel pump relay, fuel pump, and wiring connections to identify any visible damage or issues.
  2. Test the fuel pump relay and fuel pump using a multimeter to determine if they are functioning within the manufacturer's specifications.
  3. Check for any loose or corroded electrical connections in the fuel pump circuit and repair or replace them as needed.
  4. If necessary, replace the fuel pump relay, fuel pump, or any damaged wiring to resolve the low fuel pump secondary circuit issue.
  5. Clear the DTC from the PCM memory using a scan tool and test drive the vehicle to ensure the problem has been resolved.

Cost to Fix P0231 Mercury

The typical repair costs for addressing a P0231 code on a Mercury vehicle can range from $200 to $500, depending on the specific cause of the issue and the cost of parts and labor in your area. This estimate includes the cost of diagnostic testing, replacement parts (such as a fuel pump relay or fuel pump), and labor charges. Keep in mind that labor rates at auto repair shops can vary, so it's advisable to check with local shops for more accurate pricing information.

What does this mean?

Tech Notes for P0231 Mercury

For some models:

1. Disconnect the inertia switch harness connector

2. Turn key to ON position (Engine OFF)

3. Measure voltage of circuit between inertia switch harness connector and ground

4. If battery voltage is found, replaced Inertia Switch

5. Clear codes.

When is the Code Detected?

The code will be set if a low voltage on the control circuit of the fuel pump relay is detected by the ECM.

Need more information about the P0231 Mercury code?

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Need Help with the Code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0231 Mercury Code

1. What are the common symptoms of OBDII code P0231 in a Mercury related to the fuel pump secondary circuit?

- Common symptoms include engine stalling, no start condition, rough idling, and a lack of power while driving.

2. What are the typical causes of the OBDII code P0231 in a Mercury, indicating a low fuel pump secondary circuit?

- The typical causes include a faulty fuel pump, damaged wiring or connectors in the circuit, a blown fuse, or a problem with the fuel pump relay.

3. How can I diagnose the OBDII code P0231 in my Mercury indicating a low fuel pump secondary circuit?

- The diagnosis involves checking the fuel pump operation, inspecting the wiring and connectors for damage, testing the fuel pump relay, and ensuring proper fuse functionality.

4. What are some repair tips for addressing the OBDII code P0231 in a Mercury due to a low fuel pump secondary circuit?

- Repair tips include replacing a faulty fuel pump, repairing or replacing damaged wiring or connectors, checking and replacing the fuel pump relay if necessary, and resetting the trouble code after repairs.

5. Can a DIY enthusiast fix the OBDII code P0231 in a Mercury related to a low fuel pump secondary circuit?

- Depending on their skill level and access to tools, a DIY enthusiast may be able to diagnose and repair this issue, especially if it involves tasks like checking fuses, relays, and basic wiring connections.

6. How serious is the OBDII code P0231 indicating a low fuel pump secondary circuit in a Mercury?

- This code is serious as it directly affects the fuel delivery system, which can lead to engine performance issues, stalling, and potentially leaving you stranded if not addressed promptly.

7. Can driving with the OBDII code P0231 in a Mercury due to a low fuel pump secondary circuit cause further damage?

- Continuing to drive with this issue can potentially cause damage to the fuel pump or other components in the fuel delivery system, leading to more extensive and costly repairs.

8. Are there any preventive measures to avoid encountering the OBDII code P0231 related to a low fuel pump secondary circuit in a Mercury?

- Regular maintenance, such as inspecting and replacing the fuel pump as recommended by the manufacturer, can help prevent issues that might trigger this trouble code.

9. How much does it typically cost to repair the OBDII code P0231 in a Mercury caused by a low fuel pump secondary circuit?

- The cost of repair can vary depending on the exact cause of the issue, but it may involve expenses for parts like the fuel pump, wiring repairs, or replacements, and labor costs for the repair work.

10. Can resetting the OBDII code P0231 in a Mercury related to a low fuel pump secondary circuit solve the problem temporarily?

- Resetting the code may temporarily clear the warning light, but it will not fix the underlying issue causing the low fuel pump secondary circuit problem. It's crucial to diagnose and address the root cause for a lasting solution.

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