The powertrain DTC P0128 is triggered when the coolant temperature sensor readings indicate that the coolant hasn’t reached the correct regulating temperature within a certain timeframe. In other words, it hasn’t warmed up quickly enough. The powertrain control module (PCM) also takes into account the intake air temperature sensor readings. This code may indicate that there is a problem with the coolant thermostat.
Common causesChecking the trouble codes that have been registered by the control unit is often the first step for identifying the fault. You can perform a diagnostic scan by connecting an OBD2 scanner to the vehicle’s computer system. The DTCs listed may indicate a specific cause or other underlying problems. For example, if P0113 is on the list, you will need to check the IAT sensor before proceeding.
It might be a good idea to reset the DTCs after each step of the repair process and then do another scan after taking the vehicle for a test drive. This will help you to determine the effectiveness of your repair methods.
It is advisable to check the coolant level and the condition of the fluid in the tank. Contaminated fluid can cause the thermostat to stick and there should be enough coolant for the system to operate properly. You should top up, drain or change the fluid as required. You may also need to inspect the radiator fan.
You can check whether the sensors and wires are working properly by checking the voltage using a multimeter. Cleaning dirty electrical contacts with a special spray can help to restore the connection between components. If there is visible wire damage or a power supply issue, new wires should be installed. You will also need to replace the CTS and thermostat if they are broken.
It indicates that the coolant isn’t warming up quickly enough based on the running time of the engine, IAT data, and temperature readings.
It is usually the result of a jammed thermostat valve, radiator fan malfunctions or sensor problems, including faulty wires and contacts.
Although it may not pose an immediate safety risk, it will affect the engine’s efficiency and cause your fuel consumption to rocket. You can continue to drive but the longer you leave it, the more of a problem it will be, possibly resulting in contamination of the water and oil in the car. Theoretically, you can keep the vehicle going for around 1000 miles before fixing it.
Fault code P0128 - Coolant Temperature Below Thermostat Regulating Temperature can occur with any car but is most often found on the following cars:
If you get the code P0128 on your car, make sure that the diagnostics are carried out correctly and the error is still relevant. Check for symptoms associated with the problem and explore options for resolving it.
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