There are more sensors in your vehicle than you could possibly know. Each of these intelligent designs performs small functions that often go unnoticed, but without their presence owning a car would be a lot more hassle. Ensuring efficiency, safety and longevity of your vehicle, sensors are located in a variety of places. Here, we at Spares Box will show you just what you’ve been sleeping on, and exactly where these often overlooked parts spend their time.
Air Flow Sensor vs. Air Flow Meter
The sole purpose of an Air Flow Sensor is to monitor the volume of air entering your engine, while the Air Flow Meter is a slightly older design that performs the same task via a much simpler mechanism. It’s not uncommon for modern Air Flow Sensors to have the air temperature sensors incorporated into them as well as both are located in the engines air intake piping.
A MAP (Manifold Absolute Pressure) Sensor serves a similar purpose to the Air Flow Sensor. It gives the vehicles Engine Control Unit (ECU) an indicator of the air mass/density contained in the manifold that is about to enter the engine by comparing the pressure differences from within the manifold to the atmosphere outside. These are typically found on the engines intake manifold, after the throttle body.
Cam & Crank Angle Sensors
Cam and Crank Angle Sensors serve the same purpose as each other, the only difference is their location on the motor. An engine rotates through 720 degrees to complete one cycle. The computer needs to know where in the cycle the engine is so it can deliver fuel and produce sparks at the correct time. These sensors are located next to major rotating components and dictate the engines position in its cycle to the computer.
The Cam Angle Sensor reads off the vehicles Camshaft. These are typically (but not always) located high up on the motor. The Crank Angle Sensor is located lower down on the motor near the vehicles crankshaft. It is common for a car to either have none, one or both of these sensors.
When the air and fuel mixture within the engine is pre ignited (which can have various causes) it is referred to as pinging or knocking in reference to the sound it makes. It also causes a small shockwave to pass through the engine’s block. The Knock Sensor is typically bolted to the side of the engine and picks up these shockwaves. These shockwaves are read by the computer as small electrical signals. On V configuration engines like the LS series V8’s the Knock Sensor is typically located in the “Valley”.
Knocking is one of the quickest ways to ruin an engine so it is crucial the computer knows if this is occurring so it can adjust its ignition timing and air/fuel mixtures to combat it.
Throttle Position Sensor
As you push the accelerator pedal of your car, it opens and closes a valve in the engines airway referred to as the Throttle Body or Butterfly, controlling the airflow. This is how you determine how much work your engine is doing. Your vehicle’s computer needs to determine how much you are trying to accelerate so it can adjust the air/fuel mixture and ignition timing. The Throttle Position Sensor is located on the outside of the Throttle Body.
Oxygen Sensor / Lambda Sensor / AFR Sensor
Oxygen Sensors go by a few names such as the Lambda or AFR Sensor. These sensors are screwed into various locations in the exhaust system, typically close to the engine. A car may have from 1 to 4 Oxygen Sensors depending on its year of manufacture, engine and the computer used in the vehicle. They measure the oxygen content in the burnt exhaust gases as they leave the engine and aid the computer in calculating whether it needs to add or remove more fuel.
In later vehicles with Catalytic Converters (Cats), it’s common to have a sensor before and after the Cat. by comparing the results shown be each sensor the computer can determine if the Cat is doing it’s job of converting the harmful carbon monoxide into carbon dioxide efficiently.
Oil Pressure Switch / Sender
An engine relies on lubrication to operate smoothly and efficiently. The engines has an oil pump that rotates when the engine is running and pumps engine oil to the required areas, producing pressures of over 80-90psi in some cases. Without an oil pump, your engine’s lifespan would be reduced to a matter of minutes. For this reason, almost every car is fitted with either an Oil Pressure Gauge, light, or sometimes both. The Oil Pressure Sender will provide a varying electrical signal to operate the Gauge, whereas the Oil Pressure Switch will simply turn the dash light on when oil pressure drops below a set minimum.
The Oil Pressure Switch/Sender can be found almost anywhere on the engine and vary greatly in appearance. The most common location, however, will be in close proximity to the Oil Filter.
Oil Level Sensor
Oil Level Sensors (also known as a Sender) are a little less common. Typically located on either the Sump (at the very bottom of the engine) or low down on the block, the Oil Level Sensor usually has internal floats that sit in the oil within the Sump. If the float drops to a certain level it will cause the low oil light on the dashboard to illuminate.
Temperature Sender / Switch
Much like an Oil Pressure Switch or Sender, a Temperature Sender will typically operate the temperature light on your dashboard (and provide the same information to the ECU in some cases). The Temperature Switch will operate the temperature warning light and in some cars there will be a “Fan Switch”. This is just a temperature switch that turns the cooling fans on and off at pre determined temperatures. Located in many various places, some more common locations are near the vehicles thermostat, or on the radiator tanks.
Wheel Speed Sensor
Wheel Speed Sensors are (unsurprisingly) located behind the wheels of your vehicle. Your car may have 1 to 4 of these sensors.
The Wheel Speed Sensors have various functions. They calculate how quickly a wheel is rotating in order to drive electronic speedometers. They are also used in conjunction with Traction Control Systems, Active Yaw control Systems and ABS systems to determine wheels spinning at differing speeds therefore identifying wheel spin, partial loss of traction and locked brakes.
Air Temperature Sensor
Air Temperature Sensors are found in the air intake piping of many fuel injected vehicles. They consist of a very simple probe that sit in the direct path of the air entering the engine. It relays the air’s temperature back to the computer and allows the computer make minute adjustments to the air/fuel mixture and ignition timing.