Engine-CodesMercury – P0685 Mercury

P0685 Mercury Code - Powertrain Control Module Power Relay Control Circuit Open

Quick Answer

The P0685 diagnostic trouble code (DTC) for Mercury vehicles indicates a malfunction in the Powertrain Control Module (PCM) Power Relay Control Circuit. Common causes include Faulty power relay, Damaged wiring or connectors in the control circuit, Malfunctioning PCM. 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
P0685 Mercury indicates Powertrain Control Module Power Relay Control Circuit Open.
Common causes
Common causes include Faulty power relay, Damaged wiring or connectors in the control circuit, Malfunctioning PCM.
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.
Table of contents Created and updated by William Orellana on Sep 12, 2024
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Code P0685 Mercury Description

The P0685 diagnostic trouble code (DTC) for Mercury vehicles indicates a malfunction in the Powertrain Control Module (PCM) Power Relay Control Circuit. The PCM is the central computer that controls various functions in the vehicle, such as engine performance, emissions, and transmission. The power relay control circuit is responsible for providing power to the PCM, allowing it to function properly. When this circuit is open, it means that there is a break or interruption in the electrical connection between the PCM and the power relay, resulting in a loss of power to the PCM.

OBDII Code P0685 Mercury - Powertrain Control Module Power Relay Control Circuit Open
P0685 Mercury Code - Powertrain Control Module Power Relay Control Circuit Open

Common Causes of P0685 Mercury

  1. Faulty power relay
  2. Damaged wiring or connectors in the control circuit
  3. Malfunctioning PCM
  4. Blown fuse
  5. Electrical system issues

Symptoms of P0685 Mercury

  1. Engine misfires or hesitation
  2. Check engine light illuminated on the dashboard
  3. Reduced fuel efficiency
  4. Difficulty starting the vehicle
  5. Stalling or rough idling

How to Fix P0685 Mercury

  1. Diagnose the issue by using a scan tool to retrieve the specific DTC and perform a detailed inspection of the power relay control circuit.
  2. Inspect the power relay for any signs of damage or wear and replace it if necessary.
  3. Check the wiring and connectors in the control circuit for any breaks, corrosion, or loose connections and repair as needed.
  4. Test the PCM for proper functionality and replace it if it is found to be faulty.
  5. Reset the PCM and clear the DTC to see if the issue has been resolved. Test drive the vehicle to ensure that the symptoms have been eliminated.

Cost to Fix P0685 Mercury

The cost of repairing a P0685 code for a Mercury vehicle can vary depending on the specific cause of the issue and the labor rates in your area. On average, you can expect to pay between $150 and $400 for parts and labor. Keep in mind that rates at auto repair shops can vary, so it's a good idea to get quotes from multiple shops to find the best price. Additionally, the repair may require diagnostic time to pinpoint the exact cause of the problem, which can add to the overall cost.

Tech Notes for P0685 Mercury

Check all the Engine Control Module (ECM) fuses, if the fuses are OK, then replacing the ECM relay should take care of the problem.

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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 P0685 Mercury Code

1. What are common symptoms of OBDII code P0685 in a Mercury vehicle?

- Common symptoms include engine stalling, difficulty starting the vehicle, and illumination of the Check Engine Light.

2. What does the OBDII code P0685 on a Mercury indicate?

- The code P0685 indicates a problem with the Powertrain Control Module (PCM) power relay control circuit being open.

3. What are possible causes of the P0685 code in a Mercury?

- Possible causes include a faulty power relay, damaged wiring or connectors in the power relay circuit, or issues with the PCM itself.

4. How can I diagnose the P0685 code in my Mercury?

- Diagnosing the code involves inspecting the power relay, checking the wiring and connectors for any damage, and testing the PCM for proper functioning.

5. Can I still drive my Mercury with the P0685 code present?

- It is not recommended to drive the vehicle with the P0685 code present, as it can lead to more serious issues and potential engine damage.

6. How can I repair the P0685 code in my Mercury?

- Repairing the P0685 code may involve replacing the faulty power relay, repairing or replacing damaged wiring or connectors, or reprogramming the PCM.

7. Is it possible to reset the P0685 code in a Mercury without fixing the underlying issue?

- While you can clear the code temporarily, it will likely reappear until the underlying issue with the power relay control circuit is resolved.

8. Can a DIY enthusiast fix the P0685 code in a Mercury?

- Depending on your skills and experience, you may be able to diagnose and repair the P0685 code yourself, but it is recommended to seek professional help for accurate diagnosis and repair.

9. How much does it cost to repair the P0685 code in a Mercury at a mechanic?

- The cost of repairing the P0685 code can vary depending on the underlying issue, but it may range from $100 to $500 or more, including parts and labor.

10. Will fixing the P0685 code improve the performance of my Mercury?

- Yes, resolving the P0685 code will help restore proper engine function, improve performance, and prevent potential damage to other components in the vehicle.

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