AutoCodes – Hyundai – P0128 Hyundai

P0128 Hyundai 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 Hyundai 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 49,421

How popular is this code, among other codes? Medium

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 14, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0128 Hyundai 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 Hyundai - Coolant Thermostat - AutoCodes.com — P0128 Hyundai Code - Coolant Thermostat

What does this mean?

What are the Possible Causes of the DTC P0128 Hyundai?

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 Hyundai?

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

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0128 Hyundai 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.

Need more information about the P0128 Hyundai 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 P0128 Hyundai Code

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

The common symptoms include the engine running colder than normal, slow engine warm-up, poor fuel economy, and the Check Engine light illuminating.

2. What are the possible causes of OBDII code P0128 in a Hyundai?

The most common causes are a faulty thermostat, low coolant level, a malfunctioning coolant temperature sensor, or issues with the cooling system.

3. How can I diagnose the OBDII code P0128 in my Hyundai related to the coolant thermostat?

Diagnosing the code involves checking the coolant level, inspecting the thermostat and temperature sensor, and testing the cooling system for proper operation.

4. Can I still drive my Hyundai with OBDII code P0128 related to the coolant thermostat?

It is not recommended to drive the vehicle with this code for an extended period, as it can lead to overheating and potential engine damage. It is best to address the issue promptly.

5. How do I repair OBDII code P0128 in my Hyundai caused by an issue with the coolant thermostat?

The most common repair involves replacing the thermostat, ensuring proper coolant levels, and checking for any leaks in the cooling system.

6. Are there any DIY tips for addressing OBDII code P0128 in a Hyundai related to the coolant thermostat?

While some basic checks can be done at home, it is recommended to have a professional mechanic diagnose and repair the issue to ensure proper functioning of the cooling system.

7. Will resetting the Check Engine light resolve OBDII code P0128 in my Hyundai related to the coolant thermostat?

Resetting the light may temporarily turn it off, but it will not fix the underlying issue causing the code. It is essential to address the root cause of the problem.

8. Can a faulty coolant thermostat impact the overall performance of my Hyundai?

Yes, a faulty coolant thermostat can affect the engine's performance, fuel efficiency, and emissions output by not allowing the engine to reach its optimal operating temperature.

9. How often should the coolant thermostat be inspected and replaced in a Hyundai?

It is recommended to have the coolant thermostat inspected during regular maintenance intervals and replaced if any issues are detected. Typically, they can last for several years before needing replacement.

10. Is OBDII code P0128 related to the coolant thermostat a common issue in Hyundai vehicles?

Yes, OBDII code P0128 related to the coolant thermostat is a common issue in Hyundai vehicles, especially as they age and the cooling system components wear out. Regular maintenance can help prevent this code from occurring.