Complete Guide: Engine Sensors & Switches

There are many electronics & electrical components in association with the engine management system of a modern vehicle. The sensors, relays, and actuators work together for the proper functioning of a car’s engine. These sensors and components are a vital source of information for the Engine Control Unit, which then acts accordingly to give the optimal output from the engine. To sum up, in simple words, these sensors act as a bridge between the engine and other car systems so that all work in coordination. There are many sensors that directly or indirectly affect the engine functions and thus, are needed to be understood accordingly.

The major sensors governing the proper functioning of a vehicle engine are mentioned as below:

1. The Mass Air Flow Sensor - The Mass Air Flow Sensor or simply the MAF Sensor is a control module handled sensor which is used to calculate the density and volume of the air intake by the engine for combustion. This helps in maintaining a proper air-to-fuel ratio for the best output of energy. If this sensor becomes faulty, the fuel ratio may change, leading to less or more fuel entering the engine, causing stalls or overconsumption of fuel respectively.

2. The Engine Speed Sensor - The Engine Speed Sensor works in association with the crankshaft and monitors its speed of spinning to control the fuel injection and engine timing. This ensures proper functioning of the engine, preventing any stalls and stops.

3.  Oxygen Sensor - The oxygen sensor is important to maintain optimal fuel-to-air ratio in the engine as it helps in determining whether the fuel is burning rich or lean by measuring the amount of unburnt oxygen present in the exhaust pipe. Thus, this sensor, if at fault, may lead to fuel over consumption, poor idle, stalling, and indefinite stops.

4.  Manifold Absolute Pressure Sensor - The MAP or Manifold Absolute Pressure Sensor is used to detect the load on the engine. Mounted on the intake manifold, this sensor is used to determine the difference in pressure in the intake manifold and outside, so that the engine can adjust the fuel injection accordingly.

5.  Spark Knock Sensor - The knock sensor ensures smooth combustion in the engine pistons. If the combustion is not smooth, it may cause head gaskets to fail, piston rings to break, and crack, along with heavy damage to the rods. These repairs can be costly for the user.

6.  Fuel Temperature Sensor - The Fuel Temperature Sensor ensures that the fuel is at an optimal temperature before it goes for burning. Cold fuel will have a higher density and may not burn effectively. It also ensures that the right amount of fuel is injected for the proper functioning of the engine and all other related components as improper fuel supply may cause hefty damages.

7.  Voltage Sensor - The idle speed of the vehicle is managed by the voltage sensor. It ensures smooth acceleration and deceleration for the proper functioning of the vehicle.

Before any diagnosis, one must know what is the function of each sensor, its location, and point to keep in mind before diagnosing any problem concerning that sensor.

1.   Oxygen Sensor - The Oxygen Sensor or The O2 Sensor is in the exhaust system, near the exhaust manifold, after the catalytic converter. It is used to measure the oxygen content present in the exhaust gas released from the engine after the combustion process. The content of oxygen measured here is then compared to the optimal levels required for burning to determine whether the engine is running rich or lean. This further helps the fuel delivery system and emission control system to adjust their outputs. 

2.  Engine Speed Sensor - The Engine Speed Sensor is used to measure the crankshaft rotational speed in RPMs. Also known as Hall Effect Sensor, it contains a serrated disk and a magnetic coil. When the crank spins, the current and magnetic field flows through the coil. These fields are disrupted by the disk, resulting in the counts for the RPMs. Any problem in the speed sensor can be shown by speedometer or cruise control issues, ignition problems, etc.

3.  Mass Air Flow (MAF) Sensor - The MAF Sensor is used to monitor the air entering the engine as it passes through the air filters. The drivetrain computer then uses the density and volume data to determine the fuel metering and delivery. If the MAF sensor goes faulty, it may cause rich or lean engine conditions leading to rough idles, stalling, hesitation, and Check Engine Light turning on.

4.  Fuel Temperature Sensor - A fundamental truth is that the higher the density of fuel, the lower is the rate of combustion, and the lower the density, the higher will be the rate of combustion. This is where the fuel temperature sensor comes in. It measures the temperature of the fuel entering the engine to determine its density and to see if the fuel is at an optimal temperature for 100% combustion. If the fuel is too warm, the injectors may deliver more fuel to the engine leading to timing offset and opposite can cause stalls, unburnt fuel conditions, and more. Early signs of faulty sensors include increased fuel consumption and Check Engine Light on.

5. Manifold Absolute Pressure (MAP) Sensor - The MAP Sensor is used to measure the vacuum pressure in the intake manifold to take note of the engine load. This helps the Engine Control Unit to map out the spark advance and manage the fuel delivery system.

The above sensors are among the most important sensors that govern the drivability, performance and emission control of the vehicle. But there are many more sensors in the vehicle with their significance. Thus, always take the correct measure by diagnosing these sensors and taking professional help when needed.

The sensors play a vital role in connecting various systems in the vehicle to work collectively for optimal output. These sensors handle various systems like fuel delivery, engine parts, transmission control, emission control, alternators, throttle control, cruise control, and many more.

Thus, it can be very difficult to operate the vehicle for them to work properly. Thus, the following are the symptoms associated with these sensors, which can help the driver determine the problem and get it fixed before any major damage occurs.

1.  Oxygen Sensor - Faulty oxygen sensor may cause various drivability issues as hard starting, poor and rough engine idles, poor handling, jerking, and throttle issues. There can also be high fuel consumption problems along with the Check Engine Light turning on.

2.  Knock Sensor - It is important to know that this sensor shows problems under high load conditions, especially when driving on highways when we have high demands from the engine. Sudden loss of acceleration and poor fuel economy are the prime symptoms. Other symptoms may include loud noises and vibrations from the vehicle engine.

3.  MAP Sensor - The major problem of faulty MAP sensor occurs because of contamination from dust and debris in the sensor coil and wiring. This may lead to rough engine idles and hard stalling. Thus, consult a professional mechanic to diagnose this problem and keep a regular check on the wiring of various components.

4. Coolant Sensors - The coolant sensors ensure that the various components are at optimal temperatures for operation. If the coolant sensors go haywire, the engine might not run properly, leading to erratic starts, cold starts, stalling, engine rich or lean conditions leading to more fuel consumption and hampering the exhaust system showed by black smoke coming from the exhaust pipe.

It is said that a workman is only as good as his tools, and it is true for the car bodywork. It is vital to have the right tools to repair your Engine Sensors or else a straightforward job would turn into constant headaches. So that’s why we have listed out some invaluable tools below which you will need while repairing your Engine Sensors.

• New sensors or switches
• Jack/floor jack
• Jack stands
• Multimeter (optional)
• Ratchet wrench or open-end wrench
• Auto diagnostic scanner/reader
• Screwdriver

Most people have a nature to avoid risk and seek safety. That is the reason they would go with a familiar auto parts brand rather than a new one. It would prove safe, and they know what to expect. Have a look at our top brands for Engine Sensors which would offer safety and decrease the risk of disappointment.

• Blue Streak (Hygrade Motor) Engine Sensors
• Cardone Industries Engine Sensors
• Bosch Engine Sensors
• Beck/Arnley Engine Sensors
• Standard/T-Series Engine Sensors
• Spectra Premium Industries Engine Sensors
• Richporter Technology Engine Sensors

The brighter you are, the more you have to learn! That’s why we are here to provide you with more knowledge about the related parts of the car Engine Sensors. They are mentioned below:

• Crank Position Sensor
• Cam Position Sensor
• New Air Mass Sensor
• Speed Sensor
• Knock Sensor

Engine Sensors replacement cost can differ widely depending on the application, the brand of the Engine Sensors as well as who does the work. All you have to do is to replace your faulty Engine Sensors with us online and then you can leave your car to the mechanic and pick it up a few days later. Just be sure that the car mechanic is highly skilled and has an excellent reputation. Sometimes the additional service level might cost you more than what you have expected. We also recommend you to take pictures of your car before you leave it with them so that you are sure that later on it is returned to you in an unharmed condition.

• The average cost for a mass airflow sensor replacement is between $269 and $387. Labor costs are estimated between $38 and $48 while parts are priced between $231 and $339. The estimate does not include taxes and fees.
• To replace the speed sensor, you are going to pay, on average, between $330 and $380. The labor should only cost you between $80 and $100, while parts will run you about $265.
• If you decide to do the repairs, the cost to replace the oxygen sensor yourself can be between $20-$94, depending on the brand and type of sensor you buy. To have the repairs done by a mechanic the price can be anywhere between $113 to $478 for parts and labor.
• The average cost for a MAP sensor replacement is between $149 and $188. Labor costs are estimated between $45 and $58 while parts are priced between $104 and $130.The estimate does not include taxes and fees.
• The good news is that it won’t cost you an arm and a leg to replace a bad knock sensor. If you have a standard economy vehicle, you can expect to pay anywhere from $120 to $500 for replacing your knock sensor. The parts cost will be anywhere from $65 to $200, while the labor costs will be anywhere from $50 to $350.
• The average cost for a fuel temperature sensor replacement is between $287 and $345. Labor costs are estimated between $220 and $278 while parts are priced at $67.

Note about price: The cost of this service or repair can vary by location, your vehicle's make and model, and even your engine type.