P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
Technical Description
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles. Brands of vehicles that may see this code include but are not limited to Pontiac, Toyota, Mazda, Dodge, Chevrolet, Honda, Jeep, Ford, VW, etc. Although generic, the specific repair steps may vary depending on make/model.
This means that the engine’s powertrain control module (PCM) has detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. Often, the intent of the P0128 code is to indicate a faulty thermostat (likely stuck in the open condition). Similar codes: P0125
In determining that the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.
Symptoms
You will likely not notice any drivability problems other than the MIL illumination. In some cases you may experience symptoms such as:
A photo of a typical thermostat:
Causes
A code P0128 may mean that one or more of the following has happened:
Possible Solutions
Note: Please be sure the engine is turned off and cool when doing work on the cooling system. When the engine is warm, the cooling system is pressurized and very hot and can cause burns or other personal injuries if you are not careful.
Past experience indicates that the most likely solution for a P0128 is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:
Regardless of what vehicle year, make and model, it is advisable to check for TSBs because if there is a known fix set out by the automaker, it can save you time and money in the diagnosis and repair.
Other ECT sensor and circuit related DTCs: P0115, P0116, P0117, P0118, P0119, P0125
Need help?
Let us fix your problem. You are most welcome our diagnosis experts have in most cases the knowledge and skills to find the cause of the error code p0128 and to solve the problems.
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"Delete Error Code Permanently, Disable DTC Error Code Function for p0128 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p0128 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0128.
