Switches & Sensors
Engine Sensors Explained
Question: Do you know the difference between a crank angle sensor and a primary engine position sensor? If not you could be missing sales. The answer is – they are generally the same. In fact, due to the multi-functionality and the variety of locations for this sensor, it has many function related names which are used interchangeably.
Glossary of terms
Sensor Name Location
> Crank sensor > Crank
> Cam sensor > Cam
> Primary Engine Position sensor > Crank
> RPM sensor > Crank
> Cam/Crank Angle sensor > Cam/Crank
> Flywheel sensor > Crank/Flywheel
> Engine Speed sensor > Crank
The components listed above are actually derivatives of the same family of sensors, which measure the position and speed of engine components as part of the electronic fuel injection system. Yet, different component, vehicle and diagnostic equipment manufacturers use different terminology to explain the function and also the position of the sensor.
There is a lot of confusion in the aftermarket regarding this family of sensors. This confusion, which stems from a lack of knowledge regarding engine management parts and systems, can have a detrimental effect on sales at both factor and garage level. In essence, if you do not know what the part is called, you cannot sell it.
Since the introduction of electronic fuel injection, sensors have been used to monitor and communicate the engine position to the engine control unit (ECU). Using these measurements, the ECU can trigger or retard fuel injection and ignition relative to the engine’s operating conditions.
In the early days the ignition timing and the injection system were controlled by a cam sensor and the distributor.
Now, engines with direct fuel injection and coil packs or coil rails use a crank sensor, which relays the engine position to the ECU. This tells the injection system to inject fuel into the relevant cylinder. The sensor output can also be used to determine the current combustion cycle, which is very important when the engine is started.
The crank sensor can be used in combination with a camshaft position sensor to monitor the relationship between the pistons and valves in the engine, which is particularly important in engines with variable valve timing. The same sensor can be found in multiple locations on the engine, including the crank pulley, flywheel and camshaft.
Fault finding and diagnosis
The likely causes of crankshaft position sensor failure are: exposure to extreme heat, oil or dirt ingress from a failing seal, dust particles from the clutch, or wear over a long period of time. These factors cause the sensor to become burnt or worn.
When the sensor fails, it stops transmitting the signal which contains the vital data for the ignition and other parts in the system. This can cause faults such as the engine idling erratically, starting failure, poor starting or flat acceleration. If the engine is revved up when it has a bad or faulty sensor, it may cause misfiring, excessive engine vibration or backfiring. Cambiare recommends using a qualified technician or auto electrician when diagnosing a sensor fault.
To assist motor factors and garage owners, Cambiare (in partnership with Pierburg) has developed a technical brochure which examines individual components and systems in detail. To request your free copy please contact firstname.lastname@example.org