P0128 is a diagnostic trouble code (DTC) for the engine control module (ECM) in a Mercedes vehicle. This code indicates that the ECM has detected a problem with the engine coolant temperature (ECT) sensor circuit or the ECT sensor itself.
The ECT sensor measures the temperature of the engine coolant and sends this information to the ECM. The ECM uses this information to adjust the fuel-to-air ratio, ignition timing, and other engine control functions. If the ECM detects a problem with the ECT sensor or its circuit, it will set the P0128 code and illuminate the check engine light on the dashboard.
Possible causes of the P0128 code include a faulty ECT sensor, a damaged wiring harness or connector, a short or open in the ECT sensor circuit, and a malfunctioning ECM. To diagnose and repair the problem, a mechanic will need to use a diagnostic scanner to read the fault code and perform further testing.
It is important to properly diagnose and repair the cause of the P0128 code to ensure the proper functioning of the engine and to prevent further damage. If you are experiencing this problem, it is recommended that you bring your vehicle to a qualified mechanic for diagnosis and repair.
P0128 fault code explanation, treatment plan and elimination method
P0128 DTC, applicable to all car manufacturers, means Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) (Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)).
Tips: To quickly find the fault code, you can follow the official account of “Youjia” and reply to the fault code, such as: “P0128”, and you can get the explanation and solution of the corresponding fault code.
Background knowledge: The function of the thermostat is to close when the coolant temperature is low, and only allow the coolant to circulate in the engine to increase the speed of the car; when the water temperature exceeds the set temperature, the thermostat is opened to allow the coolant to circulate To the radiator of the water tank, effectively improve the cooling efficiency. This code indicates that the thermostat did not reach the desired engine operating temperature within the set time after the engine was started. Causes of failure include thermostat stuck open position, engine coolant temperature (ECT) sensor failure, etc.
After troubleshooting the car, the fault codes need to be cleared. When clearing the code, be sure to follow the fault code clearing method specified by the specified model, and be careful not to remove the negative ground wire of the battery casually to clear the fault code.
Otherwise, it may cause troubles in the following two aspects:
- First, the control computer of some models will lose its “historical record”. We know that the control computer of some models has an automatic memory function. , it will automatically clear the experience data stored in the random access memory (RAM), so that the performance of the car will not be good for a long period of time after maintenance, or after a period of driving, the fault codes that have been cleared will be reproduced;
- The second point is that it may cause the loss of normal functions. For example, the audio lock function is one of the common situations. In this case, the audio system needs to be repaired again if the audio system is to work normally. If this happens, it will be very troublesome.