Can You Guess the Function of a Tire Pressure Monitor Sensor?

You may have never asked yourself what is a tire pressure monitor sensor. These sensors do exactly what you’d expect; they monitor the pressure within your tires. However, because these sensors are battery powered, over time they will fail and you will need to replace or know how to repair tire pressure monitor sensors. Don’t worry too much about this, when the time comes you will be warned via the little TPMS on your dash and it is a fairly cheap fix. A little fact about tire pressure is that if you are driving on tires that are 10% under inflated, you will see a 1% decrease on your gas mileage.

As of 2007, the NHTSA requires the installation of these sensors on all vehicles. There are two types of these sensors, direct and indirect. Direct tire pressure monitoring sensors are located either inside or outside the tire and they physically measure the pressure. After doing so, they report this information to the instrument cluster of the vehicle. Newer vehicles can display real-time pressures of each tire while driving or parked. Indirect sensors on the other hand don’t actually detect the tire pressure, but they “infer” the pressure through various factors. The main factor is the rotational speed of each individual wheel. If a tire has less pressure, the diameter will be slightly smaller and in turn will spin a bit faster.

Regardless of which type of sensor your vehicle uses, if that warning light comes on DON'T just pretend its not there and put off the job. It is important, and cheap, to fix this issue. Not only can they save you a few extra dollars at the pump, but if they are working properly you will have lower emissions, increased handling of your vehicle, and you won't have to worry about failing that state inspection coming up. Also an under inflated tire is the leading cause of tire failure, so having your sensors in working order will increase your tire life.

What Does a Knock Sensor Do?

Knock sensors are the units in vehicles that monitor the pinging in the motor and help control the timing of the engine. The computer uses the input from the knock sensor along with the O2 sensors and air fuel ratio sensor to adjust the timing and fuel mixture in the pistons.

The engine in a modern vehicle has to be kept in perfect timing to ensure the top of efficiency and performance. This is done by toeing the line between running perfect and detonation. The perfect ignition of the air / fuel mixture happens at the exact moment that the piston is about to reach the top of its stroke. The timing is set this way to ensure the pressure has time to begin pushing the piston back down. When the spark plug is fired with the incorrect ignition timing or fuel mixture the pressure waves move out from the flame wall faster than the explosion itself. When this happens they impact the side wall at the incorrect time and a sound wave is created and detected. The element in the knock sensor is designed to detect this sound and alert the computer to adjust the timing.

All sensors in a vehicle are extremely important and are generally overlooked on basic maintenance. During automotive check ups it is important to remember to check the smaller parts such as sensors and filters to ensure protection from future issues.

What is a Crank Position Sensor

Modern engines run by using a number of specialized sensors such as Air Fuel Ratio Sensor or O2 Sensor units. While the air flow in an engine is extremely important there are other factors that need to be measured such as the position of all the parts of the motor at any given time.

The way this info is calculated is through sensors such as the crank angle sensor and the cam angle sensor. These units measure where the rotation angle of the crank and the cam shafts respectively. The cams and the crank must be kept in specific positions to each other since if they are not the valves will be smashed by the pistons.

The ECM controls the engine and if it detects that the cams and the crank are not in the specific location it will retard the timing or kill the engine all together. The ECM will do this to protect the motor from damage, if the timing gets too far off it can potentially damage the engine internally.

Timing also dictates how much horsepower the engine makes and how the fuel is burned. If these sensors fail the combustion of the engine can get all out of whack which is potentially dangerous. Besides the fact that the pistons can impact the valves there is the factor of detonation. This occurs when the fuel mixture is wrong and the explosion in the cylinder is not in the correct location and it takes place faster than it should. There are some instances where the combustion of the fuel takes place to quickly and in a specific location on the cylinder wall which will cause damage to the block itself. This detonation can even cause holes in the block or melting of the pistons. For all modern cars it is a good idea to check all these sensors when the car is in for service. They do play a pretty major factor in the life of a vehicles motor.