P0128 is an extension of OBD-II code P0 which indicates a problem with your car's coolant thermostat.
Yes, if the thermostat is not working correctly, it will throw a code and turn on the check engine light. The thermostat is responsible for regulating the engine's coolant temperature. If it is not working properly, the engine can overheat.
Although it may be possible to drive short distances with code P0128 set, you should get the issue fixed by a professional right away. Doing so will help ensure your vehicle keeps running at its best while also helping to prevent any additional damage.
A code reader can detect issues related to a bad thermostat by identifying specific trouble codes, such as P0128 or P0597, which indicate problems with the thermostat or the engine's temperature regulation.
P0128: Coolant Thermostat Temperature Below Regulating Temperature. When your check engine light is illuminated due to trouble code P0128, you may have an issue with your engine thermostat.
This is referred to as a permanent code. This permanent code will go away on its own after the monitor runs and passes. Until then it will be present but only when read with a scan tool and will not turn the light on. If the problem Is detected again by the computer it will first set a pending code.
P0128 is an extension of OBD-II code P0 which indicates a problem with your car's coolant thermostat.
When you set the thermostat above or below the current room temperature, you should hear a click, and the AC or furnace should kick on almost immediately. If you make changes at the thermostat and nothing happens, that's the first sign you have a bad thermostat.
Replacing a Thermostat. You'll pay between $15 and $300 for the unit in addition to labor ($65 to $100 per hour) to replace an old thermostat with a new one. However, installing a brand-new thermostat is more involved and, therefore, more expensive.
Check the coolant level: If the level is lower than the minimum, add more coolant and go for a short drive. If the code is still active, you must change the thermostat. Inspect the coolant temperature sensor: The primary coolant temperature sensor is in the cylinder head near the thermostat.
It's not recommended to unplug the coolant temperature sensor unless necessary for diagnostic purposes, as it can adversely affect engine operation and potentially cause damage if left unplugged for an extended period.
For daily drivers, coolant temperature below the OEM specification is not recommended. Most engine wear occurs when the engine is cold. Bearings, rings, and other parts are not fully expanded. These “loose” parts move around and wear faster.
You Notice Erratic Temperature Changes
If you notice sudden and erratic temperature changes from cold to hot or hot to cold, then it could be a sign that your thermostat has stopped working correctly. Get your vehicle inspected if you notice these extreme temperature changes in your vehicle interior.
If the 'Check Engine' light suddenly comes on, this could imply a hitch with the coolant temperature sensor. If the computer detects an unsavory development with the sensor's circuit or signal, it may set off the 'Check Engine' light. And the light will not go off until a specialist readily addresses the issue.
In the case of a defective thermostat, the DTC that is commonly associated with this problem is P0128. This code refers to a low coolant temperature condition, indicating that the engine is not reaching its normal operating temperature in a specified timeframe.
High temperature readings
The main symptoms of a failing thermostat are related to engine overheating. It can be easily noticed because the temperature gauge in the vehicle will probably read unusually high. This can be caused by the valves being stuck in a closed position.
Most modern thermostats will have a clearly marked reset button inside the panel. It's usually small and recessed, so you might need a pointed object like a paperclip to press it. For those wondering specifically how to reset air conditioner thermostat models, the process is generally the same.
An engine that is running too cool will store a P0125 or a P0128 code. This could mean that the thermostat is stuck closed if the engine is running too hot or opening too soon if the engine is running too cold.
Signs of a Bad Thermostat
If there's no change in your home's temperature when you adjust the temperature, or the display is unlit or unresponsive, your thermostat may be broken, or the batteries need replacing.
Home thermostat error codes can vary depending on the specific model and brand of your thermostat, so it's almost impossible to list every error code you might come across. However, some error codes are common to a range of brands and models.
The sensor works by measuring the temperature that's being given off by the thermostat and/or the coolant itself. The temperature is then sent to the on-board control system.
A car thermostat is designed to last a long time – typically around 100,000 miles or 10 years. However, various factors can impact its lifespan. First, driving conditions play a role. If you regularly drive in hot weather or stop-and-go traffic, your thermostat may suffer additional stress.
When your thermostat doesn;t respond to temperature conditions in your cooling system or gets stuck in either the open or closed position, it may cause a Check Engine Light to turn on. Ensure your thermostat is in good condition in order to prevent engine damage from excess heat.