AutoCodes – Toyota – P0128 2005 Toyota Prius

P0128 2005 Toyota Prius Code - Coolant Thermostat

Quick Answer

The thermostat is a component that blocks the flow of coolant to the radiator until the engine has warmed up. 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 2005 Toyota Prius 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 5,771

How popular is this code, among other codes? Low

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 Apr 21, 2019

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0128 2005 Toyota Prius Description

The thermostat is a component that blocks the flow of coolant to the radiator until the engine has warmed up. When the engine is cold, no coolant flows through the engine. Once the engine reaches its operating temperature, the thermostat opens. The OBDII sets when the engine coolant temperature has not risen enough to open the thermostat even though the engine has run long enough. This is due to a leak in the seal or the thermostat open stuck.

OBDII Code P0128 2005 Toyota Prius - Coolant Thermostat - AutoCodes.com — P0128 2005 Toyota Prius Code - Coolant Thermostat

What does this mean?

What are the Possible Causes of the DTC P0128 2005 Toyota Prius?

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 2005 Toyota Prius?

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 there are no coolant leaks, replace the thermostat first, if problem is still there check/replace coolant temperature sensor.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0128 2005 Toyota Prius 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 2005 Toyota Prius code?

Need more information on how to fix the P0128 2005 Toyota Prius code? Get Access to Factory Service Manuals

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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 2005 Toyota Prius Code

1. What does OBDII code P0128 mean on a 2005 Toyota Prius?

- OBDII code P0128 in a 2005 Toyota Prius indicates a malfunction in the coolant thermostat.

2. What are the common symptoms of a P0128 code in a 2005 Toyota Prius?

- Common symptoms of a P0128 code in a 2005 Toyota Prius include low engine temperature, poor fuel economy, and the check engine light being illuminated.

3. What are the possible causes of a P0128 code in a 2005 Toyota Prius?

- The common causes of a P0128 code in a 2005 Toyota Prius are a faulty thermostat, low coolant level, a malfunctioning coolant temperature sensor, or a problem with the cooling system.

4. How can I diagnose a P0128 code in my 2005 Toyota Prius?

- To diagnose a P0128 code in a 2005 Toyota Prius, you can use an OBDII scanner to read the trouble code and then inspect the thermostat, coolant level, temperature sensor, and cooling system for any issues.

5. Can I continue driving my 2005 Toyota Prius with a P0128 code?

- It is not recommended to drive your 2005 Toyota Prius with a P0128 code for an extended period, as it can lead to reduced fuel efficiency and potential engine damage due to operating at incorrect temperatures.

6. How can I repair a P0128 code in my 2005 Toyota Prius?

- The typical repair for a P0128 code in a 2005 Toyota Prius involves replacing the thermostat, ensuring the coolant level is correct, checking the temperature sensor, and inspecting the cooling system for any leaks or blockages.

7. Is it possible to reset a P0128 code in a 2005 Toyota Prius without fixing the issue?

- While you can clear the code with an OBDII scanner, it is not recommended to reset a P0128 code in a 2005 Toyota Prius without addressing the underlying problem, as it may lead to further issues down the line.

8. How much does it cost to fix a P0128 code in a 2005 Toyota Prius?

- The cost of fixing a P0128 code in a 2005 Toyota Prius can vary depending on the exact cause of the issue, but it typically ranges from $150 to $400 for parts and labor.

9. Can a DIY enthusiast replace the thermostat to fix a P0128 code in a 2005 Toyota Prius?

- Yes, a DIY enthusiast with the necessary tools and knowledge can replace the thermostat to fix a P0128 code in a 2005 Toyota Prius, following a repair manual or online guides for guidance.

10. How often should the coolant thermostat be replaced in a 2005 Toyota Prius?

- The coolant thermostat in a 2005 Toyota Prius should be inspected regularly as part of routine maintenance and replaced if any issues or signs of failure are detected.