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Engine-Codes – Honda – P0128 Honda

P0128 Honda Code - Cooling System Malfunction

Quick Answer

The P0128 code in a Honda indicates a cooling system malfunction. Common causes include Faulty thermostat, Low coolant levels, Malfunctioning cooling fan. 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 Honda indicates Cooling System Malfunction.
Common causes
Common causes include Faulty thermostat, Low coolant levels, Malfunctioning cooling fan.
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 07, 2024
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Code P0128 Honda Description

The P0128 code in a Honda indicates a cooling system malfunction. This means that the engine coolant temperature is not reaching the expected level within a specified time after starting the engine or during operation. The cooling system plays a crucial role in regulating the temperature of the engine to prevent overheating, which can lead to severe damage if not addressed promptly.

OBDII Code P0128 Honda - Cooling System Malfunction
P0128 Honda Code - Cooling System Malfunction

Common Causes of P0128 Honda

  1. Faulty thermostat
  2. Low coolant levels
  3. Malfunctioning cooling fan
  4. Defective coolant temperature sensor
  5. Clogged radiator

Symptoms of P0128 Honda

  1. Check engine light illuminated on the dashboard
  2. Engine running hotter than usual
  3. Low coolant levels or coolant leaks
  4. Reduced fuel efficiency
  5. Heater not working properly

How to Fix P0128 Honda

  1. Perform a visual inspection of the cooling system for leaks or damage.
  2. Check coolant levels and top off if necessary.
  3. Test the thermostat and replace if faulty.
  4. Inspect the cooling fan operation and replace if not functioning correctly.
  5. Check the coolant temperature sensor and replace if needed.

Cost to Fix P0128 Honda

The cost of repairing a P0128 code in a Honda can vary depending on the specific cause of the issue and the labor rates in your area. On average, the repair costs for this issue can range from $100 to $400, including parts and labor. It's important to consider that additional diagnostic time may be needed to pinpoint the exact cause of the problem, which can affect the final repair costs. It's recommended to consult with a qualified mechanic to get an accurate estimate based on your vehicle's make and model.

What does this mean?

Tech Notes for P0128 Honda

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

When troubleshooting a 2000-2001 Accord or 2001-2002 Civic, if the PGM Tester tells you there is a DTC P0128 (Cooling System Malfunction) or P1486 (Cooling System Malfunction) set, it's really reporting the same thing. DTC P0128 is an SAE or generic Diagnostic Trouble Code (DTC) while P1486 is a manufacturer-specific DTC. Since these DTCs are similar, the PGM Tester sometimes reports a P0128 when it detects a P1486 or vice versa.









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Information for Specific Honda 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 Honda Code

1. What does the OBDII code P0128 mean on a Honda?

P0128 indicates that the engine coolant temperature is not reaching the expected level within a specified time, suggesting a potential cooling system malfunction.

2. What are the common symptoms of code P0128 in a Honda?

Symptoms include the check engine light turning on, poor fuel efficiency, underperforming heater, or the temperature gauge reading lower than normal.

3. What causes the P0128 code on a Honda?

Common causes include a stuck-open thermostat, low coolant levels, a faulty coolant temperature sensor, or issues with the engine control module (ECM).

4. Can you drive a Honda with a P0128 code?

Yes, you can drive with a P0128 code temporarily, but prolonged driving may result in increased fuel consumption and potential engine wear due to improper operating temperatures.

5. How do you fix a P0128 code on a Honda?

The most common fix is replacing the thermostat. Other potential repairs include topping off or replacing coolant, checking the coolant temperature sensor, or inspecting the wiring and connectors.

6. How much does it cost to fix a P0128 code on a Honda?

Replacing the thermostat typically costs between $150 and $300, depending on the model and labor rates. Other repairs, such as replacing the coolant temperature sensor, may cost less.

7. Can low coolant cause a P0128 code on a Honda?

Yes, low coolant levels can prevent the engine from reaching optimal operating temperatures, triggering the P0128 code.

8. What tools are needed to diagnose a P0128 code on a Honda?

You’ll need an OBDII scanner, a thermometer or infrared temperature gun to measure coolant temperature, and basic hand tools for inspecting and replacing components.

9. How does a stuck-open thermostat cause the P0128 code?

A stuck-open thermostat allows excessive coolant flow, preventing the engine from warming up to its proper operating temperature.

10. Can a faulty coolant temperature sensor trigger the P0128 code on a Honda?

Yes, if the coolant temperature sensor sends incorrect readings to the ECM, it may mistakenly trigger the P0128 code.

Discuss the causes and fixes for P0128 Honda OBDII Code

Submit a New Comment

  • I have Honda civic 2011 and i am facing a very big challenge any time I fill the coolant container water and i drive the car for about 20 minutes I experience water shortage in the coolant container I have done the necessary checks on the radiator and pipes in the engine.I have changed the thermostat but still not ok what should I do now

    Reply to Comment

  • Are there any coolant leaks?
    If no leaks are found, then you may have a blown head gasket.

    Reply to Comment