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P0126 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


The trouble codes serve as essential indicators of possible malfunctions within the vehicle systems in the world of automotive diagnostics. The P0126 DTC (Diagnostic Trouble Code) is one such code that relates to the Engine Coolant Temperature (ECT) sensor range or performance problem. It is important to understand the significance and impact of P0136 on your vehicle’s performance so that it can be efficiently diagnosed as a cause of any problems.


The P0126 code specifically states that the Coolant Temperature ECT sensor is not able to reach the anticipated range within a defined period of time following engine start-up, which may be due to some kind of problem. The ECT sensor shall be responsible for monitoring the engine’s temperature and transmitting it to the Engine Control Module (ECM). This information will be used by the Engine Control Module to regulate engine performance and ensure that temperatures are properly controlled.


The P0126 error code can be caused by a number of things:

  • Faulty ECT Sensor: If the ECT sensor is malfunctioning, the ECM may get inaccurate temperature measurements.
  • Stuck Thermostat: If the thermostat isn’t working properly, the engine may take longer than planned to achieve the correct operating temperature.
  • Low Coolant Level: The accuracy of the ECT sensor may be impacted by a low coolant level in the cooling system.
  • Coolant Leaks: Any cooling system leaks might result in erratic coolant levels and temperature swings.
  • Wire Issues: Signal interruptions may be brought on by corroded or damaged wire that connects the ECT sensor to the ECM.
  • Connector Problems: Corroded or loose connectors may prevent the ECT sensor and the ECM from properly communicating.


You may notice a number of symptoms when the P0126 code is activated that point to possible problems with your car:

  • Illuminated Check Engine Light: The most apparent sign of a trouble code, the check engine light is activated.
  • Poor Engine Performance: Due to inaccurate temperature measurements, the engine may have reduced power, hesitancy, or rough idling.
  • Excessive heating or cooling: If the engine temperature gauge fluctuates wildly, there might be a cooling system issue.
  • Reduced Fuel Efficiency: Inaccurate temperature data might result in fuel-to-air ratios that are less than ideal, which reduces fuel efficiency.


A methodical strategy is needed to correctly identify the P0126 code’s root cause. The following diagnostic procedures can be carried out by a skilled mechanic or an OBD-II scanner:

  • Checking for Codes: The P0126 code may be read and retrieved from the vehicle’s ECM using an OBD-II scanner.
  • Visual Inspection: To find any obvious problems, the ECT sensor, it’s wiring, and its connections must be thoroughly inspected visually.
  • Testing the ECT Sensor: The resistance and voltage output of the sensor should be measured with a multimeter in order to evaluate its performance.
  • Checking Coolant Level and System: To make sure the cooling system and coolant level are within the acceptable limit, the technician will examine them.

Common mistakes

Some typical errors can happen during diagnostics and repairs, resulting in inaccurate or inefficient fixes:

  • Ignoring wire and Connectors: A loose connector or broken wire is frequently the cause of problems but is frequently disregarded.
  • Replacing the ECT Sensor Without Testing: Before contemplating a replacement, the sensor’s operation must be properly tested.
  • Ignoring Cooling System Issues: Cooling system problems should be resolved since they may affect the readings from the ECT sensor.

How serious is this?

The seriousness of the P0126 code is determined by a number of factors. While such an inconvenience may appear small, leaving the issue unresolved could have a negative effect on engine performance and potentially dangerous driving conditions. In addition, engine damage can develop as time goes by if the temperature control of the engine is not properly maintained. In order to prevent further complications, it is appropriate to diagnose and repair the condition as soon as possible.

What repairs can fix the code?

repair manuals

The following remedies can be made if the P0126 code’s underlying cause has been found:

  • Replacement of the ECT Sensor: If the sensor is broken, a suitable and superior replacement should be used.
  • Thermostat Replacement: To guarantee adequate engine temperature management, the thermostat should be replaced if it is stuck open or closed.
  • Fixing wires and connections: If required, damaged wires or connections should be fixed or replaced.
  • Repairing Coolant Leaks: To maintain optimum coolant levels, any cooling system leaks should be fixed.

Related codes

Occasionally, other DTCs might accompany the P0126 code, providing additional insights into related issues. Commonly related codes include P0116 (Engine Coolant Temperature Circuit Range/Performance Problem) and P0117 (Engine Coolant Temperature Circuit Low Input).


The code P0126 DTC suggests potential trouble with the temperature range or performance of the engine’s Coolant Temperature Sensor. It may help to understand the problem, its causes, symptoms, and necessary remedies so that it can be effectively addressed. 

In addition to clearing the code, rapid diagnosis and correct repair will also ensure that your vehicle runs at its optimum performance, resulting in a smoother and safer driving experience. In order to maintain the highest possible quality of your vehicle, you must ensure that you consult with an expert mechanic for proper diagnosis and safe repairs.

P0126 Code – What Does It Mean & How To Fix It