P0128 Code (Meaning, Causes, Symptoms & Fixes)

P0128 Code (Meaning, Causes, Symptoms & Fixes)

Dream Cheeky will help you know How To Fix P0128 Code 2022: Best Guide

Video How To Fix P0128 Code

When your check engine light is illuminated due to the P0128 code, you may have an issue with your engine thermostat. you should take these steps to fix the P0128 code. This article will help you to fix your thermostat and solve this problem code.

Many drivers ignore codes that lighten the Check Engine light but don’t have obvious symptoms. This strategy has a flaw.

Unless you have an active misfire (it flashes when it is severe enough), the MIL lights only know how to notify you of a problem; it doesn’t tell how many problems the ECM/PCM has found.

For example, let’s say you go to the parts shop or use your scanner. You get a P0128 engine Code and think you will take care of it later. But when “later” finally arrives, you find that you have five or six other problems besides the one that illuminated the check engine light.

The engine control module (ECM), which tracks the time it takes for a vehicle’s engine to reach the operating temperature, monitors this temperature.

The powertrain control module commands the fuel system to enter “closed-loop,” where oxygen sensor readings are used to maintain a 14.7:1 ratio.

ECMs require that the Engine coolant temperature sensor records temperatures beyond 160 F within 15 minutes after the engine starts.

The engine temperature recorded must not drop below 160 F after the threshold of 160 F has been reached. If any one of these criteria is not met, the PCM will report it to the PCM. Code P0128 will be triggered if either of these faults is again recorded on the next engine start.

Also Read: P0456 Code – Meaning, Causes, Symptoms & Fixes

What Causes The P0128 Code?

p0128 causes

Common causes of the P0128 code are:

  1. Faulty or sticky thermostat
  2. Coolant bypassing closed thermostats because the thermostat seal isn’t sealing properly
  3. Faulty engine coolant temperature (ECT) sensor
  4. The engine computer (PCM) software must be updated
  5. Low coolant level
  6. Radiator fan doesn’t turn off
  7. Faulty intake temperature (IAT sensor)

P0128 Code Symptoms?

These are the most common symptoms you will experience if your car is triggering the P0128 code.

  1. Check Engine Light is On
  2. Warm-up takes longer
  3. Driving on the highway causes the temperature of your engine to drop significantly.
  4. The temperature gauge indicates cooler than it usually does
  5. The heater won’t work optimally
  6. A P0128 will usually not be as noticeable due to a reduced fuel economy.
  7. Failed emissions test or monitors “not ready” for emissions testing.

How Serious Is The P0128 Code?

How Serious Is The P0128 Code
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P0128 is not considered a serious code. However, if not fixed and the car is used over a long time, there is a slight chance that water contamination of the oil could cause deterioration and engine damage. This code is set when the coolant doesn’t get hot enough.

It means that the engine is not heating up enough to burn off the condensation. That water could then end up in oil. Engine damage can occur over many years, although it is unlikely.

How To Diagnose And Repair Code P0128

  1. To verify that P0128 is the only code in your vehicle, scan it. Other codes must first be addressed.
  2. Make sure to check the coolant level. Excessive rust or poor coolant conditions can cause the cooling system to clog and the thermostat to stick. Flush the coolant system to ensure it is in good condition. Check for leaks if the coolant level drops.
  3. A Multimeter is used to check the coolant temperature sensor. The temperature will affect the ohm reading. If the ohm reading does not change with temperature, replace the coolant temperature sensor.
  4. A stuck engine coolant thermostat most commonly causes a P0128 code. This can be easily diagnosed by feeling the radiator hose to determine how hot the coolant is as it flows through the radiator. It would be best if you were more careful, as you may burn yourself. The thermostat should open when the hose is barely warm. The thermostat should open when the coolant starts to flow, as this will quickly heat the radiator. If the radiator heats slowly, it is likely that the thermostat has been prematurely opened or stuck open.

How To Fix The P0128 code?

How To Fix The P0128 code
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The following repairs can fix the P0128 code

  1. Replacing the thermostat (most common repair)
  2. Replacing the coolant temperature sensor, or also replacing the wiring and connector associated with the sensor being damaged
  3. Coolant system leaking bleeding air
  4. Check the coolant temperature and test drive it
  5. Look for leaks

Watch this video guide on how to fix the P0128 engine code

How Much Does It Cost To Fix P0128 Code

P0128 code repair costs can be anywhere from $140 to $250. The estimated repair cost for each repair is inclusive of both the labor and parts costs. Thermostat $220-$250, a Temperature sensor for coolant $140-$190. These prices may vary depending on your care make and model and your location.

Also Read: P0700 Code (Meaning, Causes, Symptoms & Fixes)

Frequently Asked Questions


The P0128 code indicates that the engine coolant is not getting heated up fast enough, which means that the engine’s operating temperature is not reaching a specified temperature within a given time. The ambient temperature determines time.

If the coolant is not at the right temperature, it can lead to poor engine performance and low fuel economy, which indicates that your thermostat is not working correctly.

As mentioned, there may be other causes of the code. If you get the code, take your vehicle to your mechanic for a check. You could possibly end up paying more for repairs in the long term if the damage spreads to other parts of your car.

You can prevent this from happening by diagnosing the symptoms of p0128 engine code early and fixing what is broken.