Red Flags of an Engine Coolant Temperature Sensor Problem in Your BMW

The coolant temperature sensor is a vital component of the engine management system of your BMW. The function of this sensor is to detect the temperature of the engine coolant and transmit this information to the computer that controls the engine.

Problems with this component may lead to inaccurate information about the coolant temperature in your car and have an adverse impact on the performance of your BMW, its fuel efficiency, starting and emissions.

What Does the Engine Coolant Temperature Sensor Do?

The engine coolant temperature sensor detects the temperature of the engine coolant that passes through it. Usually, this device transmits an electrical signal to the engine control unit depending on the temperature reading.

The engine control unit then uses the data for the following purposes:

• Adjusts the air-to-fuel ratio

• Regulates the idle speed of the engine

• Determines ignition timing

• Controls the operation of cooling fans

• Cold start operation

• Engine temperature detection

• Controls the functions related to emissions

Cold Starting Problems

BMW will have a problem with cold starting if the coolant temperature sensor is sending wrong signals to the ECU. The ECU determines the amount of fuel the engine requires based on the temperature signals.

Some of the symptoms that you can expect include:

• Longer cranking until the engine starts

• Rough running shortly after startup

• More than one attempt to start the engine

• Rough idle for the first few minutes

Poor Fuel Consumption

The fuel consumption in your BMW will also be affected by a faulty coolant temperature sensor. If the ECU gets the wrong signals about the temperature from the sensor then the ECU will wrongly mix the fuel.

As a result, your engine will be running on a rich mixture of fuel leading to poor fuel economy. If your BMW starts consuming more fuel than before without any changes in the way you drive the car then the coolant temperature sensor is one of the components to inspect.

The Temperature Reading Is Unusual

Another sign of a problem with the temperature sensor is unusual behaviour on the dashboard temperature display. Depending on your BMW model this problem may manifest in different ways through the temperature readings.

The following temperature readings may indicate issues:

• Consistently low

• Abnormally fluctuating

• Does not match the actual engine condition

• Shows an unusual reading after starting

Cooling Fan Runs at the Wrong Time

The coolant temperature sensor is crucial in ensuring that the cooling system works properly. When the signal given by the sensor is wrong then the cooling fan will work differently than expected. Sometimes the cooling fan may work for a prolonged time. This shows that there might be something wrong with the sensor.

Causes of Coolant Temperature Sensor Faults

There are several possible reasons for the malfunction of the sensor. Some of them may arise due to gradual wear and others may be the result of electrical or cooling system faults.

The most common causes of faulty sensors are:

• Gradual wear

• Faulty internal components

• Faulty wiring

• Problems with the connection

• Contamination of the coolant

• Leaking coolant near the sensor

• Corrosion on the connector

• Improper repairs

• Engine overheating

How Does a BMW Coolant Temperature Sensor Problem Get Identified?

The technician will begin by doing a computer scan of your car to see if there are any stored diagnostic codes. The check could involve checking the signal from the sensor, the wiring, the connector, coolant status and other components of the cooling system.

The technician will then compare the temperature indicated by the sensor to the actual engine temperature. This will help in determining whether the temperature reading is correct.

Ensure Optimal Performance of Your BMW With Expert Services

If your BMW shows any of these signs then professional diagnosis would be the most effective way to get to the root of the problem. The technician will first inspect the sensor, wiring, the cooling system and other components before recommending an appropriate fix.

You can count on our experts to professionally diagnose and perform other BMW repairs to ensure that your engine runs smoothly. You can visit our shop to have your BMW checked.

Masters European and Japanese Auto Repair shop is Mill Valley’s #1 European and Japanese auto repair facility in the entire area. We are one of the most sought after auto repair shops because of our performance, high safety standards.