Table of Contents
What Does A P0128 Code Mean?
Before getting into in-depth knowledge about the P0128 Code, first of all, know what does a P0128 means and how it works in your car.
Don’t worry we are here to explain how long can you drive with a P0128 code. P0128 is telling your fix sensor that your car’s coolant thermostat is operating below the regulating temperature. Or, your car’s engine is not getting hot enough fast. I know what you are thinking. Yes, a hot engine seems bad. But your car needs to heat up and reach the 160 degrees Fahrenheit to operate well. It works in a close loop to heat up fast and once It’s hot enough opens up to the radiator to work efficiently. If your car doesn’t reach open-loop, your car’s fuel economy and emission will suffer. But, if you want more detailed information, look here. It usually boils down to a faulty thermostat or temperature sensor.
Causes: Why P0128 Error Code Happens.
To tell about the causes of the P0128, at first I’d draw your attention on these points:
- Stuck open coolant thermostat
Provided that, the thermostat is removed for an extended period of time, it might show incorrect readings of the temperature. Accordingly, this inappropriate data may cause the PCM to switch on the P0128.
- Missing thermostat
If the thermostat is missing, it may even result in P0128 to be switched on. While the coolant is missing, the temperature won’t get down.
- Faulty Coolant Temperature Sensor
When the temperature sensor of the coolant shows incorrect temperature reading, this might affect the PCM to provoke the P0128 code.
- Radiator Fan
If your car has no radiator fan, then the temperature can easily be high at times. Since there is no option to cool down your engine, it can get warm. And thus the code might turn on.
- Faulty wiring for coolant temperature circuit
If the wiring for the coolant temperature circuit is deficient, it may cause the engine hotness to rise up. So, it is important to use the perfect wiring of the coolant circuits.
Signs and Symptoms of the P0128 Error Code
As you are looking for the tricks how can you fix and run with your car well, you must know what are the sign and symptoms of the P0128 Code. By knowing these factors, you will be able to perform the troubleshooting of the P0128 Code.
Therefore, read out the below points before you really start the repair. The first thing that can happen while there is some troubles with the code is:
- Taking more time to start the engine
First of all, you will find your car taking a long duration than regular to heat up. You will notice your engine’s estimated start-up time becoming higher.
- Higher than normal idle
While there are some issues, you will be able to detect that the idle is much higher than normal idle.
- The temperature gauge is unusually low
If you want to diagnose the P0128 initially, you have to keep your eyes on. See how low the temperature gauge is. Hardly, the temperature gauge can rise up in this case.
- Decreased fuel economy
While the engine is taking a lot more to warm up, there will be a decrease in the fuel economy as well. Eventually, you will get the fuel to break out more frequently. So, you will need to refuel repeatedly more than a normal situation.
- Check Engine Light is on
Last but not least, your engine light will get on. Take it as a reminder that the vehicle’s engine is not fine enough to run with.
How can you fix the P0128 problem?
Experts recommend that one should start the P0128 troubleshooting by checking out the engine’s thermostat. See whether it reaches in operating temperature or not. In general, the temperature should be 160° – 200° Fahrenheit. The question may come from the other part, how to check the thermostat operation? 
To do this, at first, start your engine and measure the temperature of the radiator hose. In the beginning, the radiator hose should be cool. But all of a sudden it might turn into a very hot condition within around 3-5 minutes. On the other hand, If there is no sudden heat up in the hose’s exterior warmth, *** then the case might be interesting. In this case, your car may have a stuck open thermostat condition. So, you’d have to replace the thermostat.
Again, while the thermostat is working properly as it did before, now you should check the engine coolant temperature(ECT) sensor. In order to check it, you will need a Voltmeter.
Keep the ignition on and put your engine off. Then check the reference voltage from the ECM to the ECT. Watch at least 5 volts consistently. After that, turn on the car engine and calculate the voltage of the ECT signal wire. If your engine heats up, the voltage will reduce. Although the estimated reading of the voltage may vary from vehicle to vehicle, usually it will be about 0.5 volts. Be concerned about the voltage reading, if there is fluctuation in voltage or not.
Make sure to measure the reading after the engine coolant temperature connector plus at the engine coolant temperature sensor itself.
Follow the below procedure step by step:
- See the coolant sock attached to the thermostat housing for an unexpected rise in temperature.
- Scan the ECT signal as well as the reference voltage.
- Make an inspection in the ECT connector.
How to Diagnose and Repair the P0128 code?
The first thing you should do for diagnosing is to scan your car and can check whether the P0128 code is existing or not. Then, check out whether there are some error codes or not. If there are some issues, you should fix them first. 
After that, scan the coolant levels and see what’s the situation of it. The coolant that comes with massive rusts is not in decent condition. You have to flush the rust as soon as possible. And if you get the coolant level low, this time you should scan for the leaks as well as scan the coolant system.
Another important thing is to check the coolant temperature sensors. If they are not working well, you have to replace coolant temperature sensors. Again, see how the radiator fan is working on. If the radiator fan is not capable enough to cool down your engine, you must replace it without any delay.
Common Mistakes Happen While Diagnosing P0128
Most of the persons who diagnose this operation without being conscious of every possible cause. So, you should scan the cooling system for rust deposits. As you can prevent rust deposits from getting squeezed in the new thermostat, you have to wash the engine block and radiator fan.
How Serious is the P0128 and is it safe to drive with it?
While in the stuck open thermostat condition, you may be in difficulty. Thermostats fail if there are stuck open. Make an inspection to fulfill the coolant system. If you overheat the engine, it will cause your engine to downfall.
How Long Can You Drive with A P0128 Code?
Honestly speaking, the P0128 code is not the most problematic code to run with. Anyway, the P0128 is safe to drive with immediately. But, if you have problems with the error code, you should not avoid this occurrence for a long time. Long time duration would let you and your car in massive trouble in the future.
That is to say, if you take too long to repair this, the problem will rise up. Therefore, it will be an intelligent decision to repair the error code as soon as it starts happening.
Note: It can be easily said that one can drive at least 500 miles even having problems with the P0128 error code. Still, it is not safe to drive more than 1000 miles. So, you should fix the error code problem before driving this far.
Cost of fixing a p0128
In order to solve the problem, you will have to rectify the basic issues that are mentioned above. So, you are to cost an amount for all probable repair. Here, the approximate cost comprises mainly two types of cost.
- Cost of the relevant parts
- Cost of labor
And the cost of:
- Thermostat: There are several products and it’s not possible to note down the exact cost. In general, you will need something around $150. Check my recommended product from Amazon.
- Coolant temperature sensor Here, you will need about a $25-$50 more to buy it.
Let’s Wrap Up the problem of a P0128 code!
You’re about to touch the finishing line. We’ve tried to let you know everything about the error code and also answered the mighty question, how long can you drive with a P0128 code. If you have any trouble with the P0128 code, then follow the mentioned technique. Hopefully, you can fix it with ease.
