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P1391 Ford Code - Glow Plug Circuit Low Input Bank 1

Quick Answer

The P1391 diagnostic trouble code (DTC) in Ford vehicles indicates a low input signal in the glow plug circuit of Bank 1. Common causes include Faulty glow plug(s) in Bank 1, Damaged wiring or connectors in the glow plug circuit, A malfunctioning glow plug controller. 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
P1391 Ford indicates Glow Plug Circuit Low Input Bank 1.
Common causes
Common causes include Faulty glow plug(s) in Bank 1, Damaged wiring or connectors in the glow plug circuit, A malfunctioning glow plug controller.
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 08, 2024
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Code P1391 Ford Description

The P1391 diagnostic trouble code (DTC) in Ford vehicles indicates a low input signal in the glow plug circuit of Bank 1. Glow plugs are essential components in diesel engines, assisting in cold starts by heating the combustion chamber. When this code is triggered, it typically means that there is a problem with the glow plug circuit on the first bank of cylinders. This issue can lead to difficulties starting the engine, especially in cold weather conditions, as the glow plugs may not be functioning optimally.

OBDII Code P1391 Ford - Glow Plug Circuit Low Input Bank 1
P1391 Ford Code - Glow Plug Circuit Low Input Bank 1

Common Causes of P1391 Ford

  1. Faulty glow plug(s) in Bank 1.
  2. Damaged wiring or connectors in the glow plug circuit.
  3. A malfunctioning glow plug controller.
  4. Issues with the ECM or PCM sending incorrect signals to the glow plug circuit.
  5. Corrosion or poor connections in the glow plug system.

Symptoms of P1391 Ford

  1. Difficulty starting the engine, especially in cold weather.
  2. Illumination of the check engine light on the dashboard.
  3. Rough idle or misfires during startup.
  4. Reduced engine power or acceleration.
  5. Increased fuel consumption.

How to Fix P1391 Ford

  1. Perform a comprehensive diagnostic scan to confirm the P1391 code and identify the specific glow plug(s) or circuit components causing the issue.
  2. Inspect the glow plugs, wiring, and connectors in Bank 1 for any visible damage or wear.
  3. Test the glow plug controller and ECM/PCM for proper functionality.
  4. Replace any faulty glow plugs, wiring, connectors, or control modules as needed.
  5. Clear the DTC and reset the ECM/PCM to ensure the code does not reappear.

Cost to Fix P1391 Ford

The cost of repairing a P1391 code in a Ford vehicle can vary depending on the extent of the issue and the specific components that need replacement. On average, the repair costs for this issue can range from $200 to $500, including parts and labor. It's important to note that prices may differ based on the location, vehicle model, and labor rates at auto repair shops. Always consult with a trusted mechanic or dealership to get an accurate estimate for addressing the P1391 code in your Ford vehicle.

What does this mean?

Tech Notes for P1391 Ford

California trucks it has a GPCM (Glow Plug Control Module) instead of a GPR (Glow Plug Relay).

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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 P1391 Ford Code

1. What are the common symptoms of OBDII code P1391 Ford related to the Glow Plug Circuit Low Input Bank 1?

- Common symptoms may include rough idling, difficulty starting the engine, reduced fuel efficiency, and an illuminated check engine light.

2. What are the possible causes of OBDII code P1391 Ford indicating a Glow Plug Circuit Low Input Bank 1 issue?

- Possible causes include faulty glow plugs, damaged wiring or connectors in the glow plug circuit, a malfunctioning glow plug control module, or a problem with the engine control unit (ECU).

3. How can I diagnose the underlying issue causing OBDII code P1391 Ford to appear for the Glow Plug Circuit Low Input Bank 1?

- A thorough diagnostic process may involve checking the glow plugs for continuity, inspecting the wiring for any signs of damage, testing the glow plug control module, and scanning the ECU for any related error codes.

4. Is it safe to continue driving with OBDII code P1391 Ford triggered by a Glow Plug Circuit Low Input Bank 1 problem?

- It is not recommended to drive the vehicle for an extended period with this issue, as it can affect the engine's performance and potentially lead to more severe problems if left unresolved.

5. How can I repair OBDII code P1391 Ford associated with a Glow Plug Circuit Low Input Bank 1 issue?

- Repair options may involve replacing faulty glow plugs, repairing or replacing damaged wiring, addressing issues with the glow plug control module, or reprogramming the ECU as necessary.

6. Can extreme weather conditions affect the Glow Plug Circuit Low Input Bank 1 issue triggering OBDII code P1391 Ford in a Ford vehicle?

- Yes, extreme cold weather can put additional strain on the glow plug system, potentially exacerbating existing issues and leading to the illumination of the check engine light.

7. Are there any preventive measures to avoid encountering OBDII code P1391 Ford due to Glow Plug Circuit Low Input Bank 1 problems?

- Regular maintenance of the glow plug system, including checking and replacing glow plugs as needed, can help prevent issues that may trigger this error code.

8. Can a DIY enthusiast with basic automotive knowledge troubleshoot and fix OBDII code P1391 Ford related to the Glow Plug Circuit Low Input Bank 1?

- While some troubleshooting steps can be performed by individuals with basic automotive knowledge, diagnosing and repairing complex glow plug system issues may require professional assistance.

9. Will resetting the check engine light erase OBDII code P1391 Ford linked to the Glow Plug Circuit Low Input Bank 1?

- Resetting the check engine light may temporarily clear the code, but if the underlying issue is not addressed, the code is likely to reappear once the problem is detected again.

10. How long does it typically take to resolve OBDII code P1391 Ford associated with a Glow Plug Circuit Low Input Bank 1 issue?

- The time needed to resolve this code can vary depending on the specific cause of the problem, the availability of parts, and the expertise of the technician, but it is advisable to address the issue promptly to prevent further damage.

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