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P0128 Ford Code - Coolant Thermostat

Quick Answer

Coolant thermostat (coolant temperature below thermostat regulating temperature). Common causes include Leaking or stuck open thermostat, Low engine coolant level, Insufficient warm up time. 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
P0128 Ford indicates Coolant Thermostat.
Common causes
Common causes include Leaking or stuck open thermostat, Low engine coolant level, Insufficient warm up time.
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.
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Code Popularity 117,397
How popular is this code, among other codes? Medium
What is this?
Table of contents Created and updated by William Orellana on Aug 14, 2020
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Code P0128 Ford Description

Coolant thermostat (coolant temperature below thermostat regulating temperature). Indicates that the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time after starting the engine.
OBDII Code P0128 Ford - Coolant Thermostat - AutoCodes.com
P0128 Ford Code - Coolant Thermostat
What does this mean?

What are the Possible Causes of the DTC P0128 Ford?

  • Leaking or stuck open thermostat
  • Low engine coolant level
  • Insufficient warm up time
  • Faulty engine coolant temperature sensor
  • Engine coolant temperature sensor harness is open or shorted
  • Engine coolant temperature sensor circuit poor electrical connection

How to Fix the DTC P0128 Ford?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

If the cooling system is not leaking and the fluid level is OK, replacing the thermostat usually takes care of the problem.





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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0128 Ford code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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Need Help with the Code?

Get the P0128 Ford code diagnosed by a professional: Find a repair shop in your area

Information for Specific Ford Models

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 P0128 Ford Code

1. What are the common symptoms of the P0128 Ford OBDII code related to the coolant thermostat?

- The common symptoms include the engine running colder than normal, a decrease in fuel efficiency, and the Check Engine light illuminating on the dashboard.

2. What are the possible causes of the P0128 Ford OBDII code indicating an issue with the coolant thermostat?

- The code is often triggered by a malfunctioning thermostat, low coolant levels, a faulty engine coolant temperature sensor, or a problem with the cooling system.

3. How can I diagnose the P0128 Ford OBDII code related to the coolant thermostat issue?

- A diagnostic scan tool can be used to read the code and monitor the engine coolant temperature sensor's readings to determine if they are within the specified range.

4. What steps can I take to repair the P0128 Ford OBDII code associated with the coolant thermostat problem?

- Common repair steps include replacing the thermostat, checking and topping up coolant levels, inspecting the engine coolant temperature sensor, and ensuring the proper functioning of the cooling system components.

5. Are there any DIY tips for addressing the P0128 Ford OBDII code linked to the coolant thermostat malfunction?

- DIY enthusiasts can start by checking the coolant level, inspecting the thermostat for any visible issues, and ensuring there are no leaks in the cooling system before considering professional help.

6. How critical is it to address the P0128 Ford OBDII code indicating a problem with the coolant thermostat?

- Ignoring the issue can lead to engine overheating, potential damage to engine components, reduced fuel efficiency, and increased emissions. It is advisable to address the problem promptly.

7. Can a faulty coolant thermostat cause other engine-related issues besides triggering the P0128 Ford OBDII code?

- Yes, a malfunctioning coolant thermostat can lead to poor engine performance, increased wear and tear on engine components, and potential overheating problems if not addressed in a timely manner.

8. Is it safe to continue driving my vehicle with the P0128 Ford OBDII code related to the coolant thermostat issue?

- It is not recommended to drive the vehicle for an extended period with the P0128 code present, as it can lead to potential engine damage and safety risks due to overheating.

9. How much can I expect to pay for repairing the P0128 Ford OBDII code linked to the coolant thermostat problem at a professional auto repair shop?

- The repair costs can vary depending on the exact cause of the issue, but generally, you can expect to pay anywhere from $150 to $400 for parts and labor.

10. What preventive maintenance measures can I take to avoid encountering the P0128 Ford OBDII code due to coolant thermostat issues in the future?

- Regularly checking and maintaining the cooling system, monitoring coolant levels, replacing the thermostat as recommended by the manufacturer, and addressing any cooling system issues promptly can help prevent the recurrence of the code.

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