Mobiletron has recently launched ranges of knock and brake wear sensors, with almost 100 new parts covering over 5,000 vehicle applications.
A knock sensor’s primary function is to ensure that you’re getting as much power and fuel economy as is possible from the engine. It does this by detecting incorrect detonation or pinging from the engine.
A knock is when the engine ignites the fuel and air mixture too early. This is otherwise called pre-ignition. This information is then sent to the ECU. Once the ECU has received this signal, the unit corrects the ignition parameters – for example by delaying the spark to protect the engine from possible damage. Mis-detonation is due to bad fuel, ignition problems or timing.
In case of detonation, the engine vibrates at a well defined frequency of usually between 5 and 8KHz, which is usually unique to the engine. The sensor is fitted directly to the side of the engine block, usually by a threaded sensor type or with a bolt through the sensor itself. There is usually one sensor on four cylinder engines and two sensors for six and eight cylinder engines.
Knock sensor failure symptoms
The main symptom of a faulty knock sensor is drivability problems. This is usually a lack of power and some hesitation from the engine. This will also increase fuel consumption.
What causes knock sensors to fail?
Knock sensors are very sensitive and can be easily damaged, making them instantly worthless. Corrosion from condensation is a common cause of failures. If the knock sensor fails, it can seriously damage the engine, as continuous pre-ignition can cause fracture in the pistons.
Brake wear sensors
The brake pad wear sensor is an additional safety feature on many vehicles, and is used to alert a vehicle’s driver when the brake pads are wearing thin. When subjected to high levels of friction, a brake pad will inevitably wear down. When the pad has worn to a pre- programmed point, the brake pad sensor makes contact with the metal of the brake disc and completes an electrical circuit. This action sends a signal to the dashboard in the form of a warning light.
Once a brake pad sensor has completed a circuit through contact with the rotor, it cannot be reused. Every time you change the brake pads, you also need to install a new brake pad sensor.