Understanding the Crankshaft Position Sensor(Definition, Symptoms & Testing）

Understanding the Crankshaft Position Sensor

A. Definition of Crankshaft Position Sensor

Automotive crankshaft position sensor is one of the most important sensors on the engine, its role is to detect the crankshaft Angle position and engine speed. Because in order to control the exact ignition time, the engine needs to use sensors to identify the position of the top of the compression stroke of a cylinder and compare it with the signal detected by the camshaft position sensor. If the signal obtained by the crankshaft position sensor is wrong or the crankshaft position sensor is damaged, the vehicle will have some faults such as weak acceleration, decreased engine power, unstable idle speed, and failure to start. The engine fault light is lit and the corresponding fault code is stored in the ECU(engine control computer).

B. Types of Crankshaft Position Sensor

According to the different structure and principle of the sensor, the crankshaft position sensor can be divided into three categories, namely Hall type, magnetoelectric type and photoelectric type.

At present, the main sensors used in the engine are Hall or magnetoelectric sensors.

1. Hall Style

Hall speed sensor is a magnetic sensor, the use of Hall effect to achieve the conversion of magnetic characteristics to electrical signals, by Hall components, permanent magnets, magnetic steel plate, trigger impeller, etc., with small size, easy to use characteristics. The signal voltage has nothing to do with the engine speed, and high detection accuracy can still be obtained at low speed when the engine is started. Hall sensors are different from magnetic induction sensors in that they require an external power supply.

2. Magnetoelectric type

Magnetoelectric speed sensor is mainly composed of electromagnetic coil, permanent magnet and signal wheel, it is a kind of sensor that uses the principle of magnetoelectric induction to change the magnetic flux through the coil into induced electromotive force. This kind of sensor is characterized by simple and firm structure and low cost. In addition, it has a large operating temperature range and only requires two connecting wires, so it has been widely used in automobiles.

Functions of Crankshaft Position Sensor

1. The crankshaft position sensor can detect the engine speed, determine the fuel injection amount and ignition advance Angle, and avoid the phenomenon of reduced fuel injection amount.
2. The crankshaft position sensor can detect the reference position of the engine reference cylinder and distinguish the cylinder sequence.
3. The crankshaft position sensor can detect the Angle of the crankshaft rotation, determine any position of the piston operation, determine the ignition time and fuel injection time, and help the best moment of the car ignition.
4. In addition to controlling fuel injection and ignition, crankshaft position sensor is also used for idle speed control, fuel evaporation control, etc., reasonable use of crankshaft position sensor can have a more accurate understanding of the working situation of the car.
5. Collect the crankshaft rotation Angle and engine speed signal, and input the ECU, in order to determine the injection sequence, injection timing, ignition sequence, ignition timing, and then according to the signal monitoring of the crankshaft Angle fluctuation size to determine whether the engine fire phenomenon.

Common Issues with failing Crankshaft Position Sensors

A. Symptoms of a bad Crankshaft Position Sensors

1. The engine cannot start

A faulty crankshaft position sensor may cause the engine to fail to start. This is because the crankshaft position sensor is responsible for monitoring the position of the crankshaft, and if the sensor fails, the engine control system cannot know the position of the crankshaft, and thus cannot properly light the spark plug, resulting in the engine not starting.

2. Engine stall

Crankshaft position sensor failure can also cause engine stall. When the sensors fail, the engine control system may not get accurate information about the crankshaft position and thus cannot properly control the fuel injection and ignition timing, causing the engine to stall.

3. The engine shakes abnormally

Crankshaft position sensor failure can cause abnormal engine jitter. Sensor failure will cause the engine control system can not accurately control the fuel injection and ignition timing, resulting in unstable engine operation and abnormal jitter.

4. Poor acceleration

A faulty crankshaft position sensor can also cause poor vehicle acceleration. Due to the sensor failure, the engine control system cannot accurately control the fuel injection and ignition timing, resulting in weak or poor acceleration of the vehicle.

B. Crankshaft position sensor code

A crankshaft position sensor code refers to a specific diagnostic trouble code (DTC) that is triggered when the vehicle's computer detects a problem with the crankshaft position sensor.   These codes can help technicians identify and fix problems with the sensor. Here are a few common crankshaft position sensor codes:

1. P0335:The diagnostic trouble code (DTC) P0335 is related to the crankshaft position sensor "A" circuit.  This code is triggered when the vehicle's powertrain control module (PCM) or engine control module (ECM) detects a problem with the signal coming from the crankshaft position sensor. When a P0335 code is triggered, it usually indicates that the crankshaft position sensor may be faulty or malfunctioning, or that there may be a problem with the wiring or connectors associated with the crankshaft position sensor, such as a short or open circuit, or a mechanical problem with the engine itself, such as a timing belt or chain problem.
2.   P0336:The Diagnostic Trouble Code (DTC) P0336 is set by the car's computer when it detects an issue with the Crankshaft Position Sensor "A" Circuit Range/Performance.When the P0336 code is set, it means the ECM or PCM has detected that the signal from the crankshaft position sensor is outside of the normal expected range, which could indicate an issue with the sensor itself or with the circuit.Some common symptoms of a P0336 code can include Difficulty starting the car, Engine misfires or stalling, Reduced engine performance and The Check Engine Light turns on, etc.

Testing and Replacing a Crankshaft Position Sensor

A. How to Test a Sensor

1. Check the cable connecting the sensor

The crankshaft position sensor failure may be caused by a fault in the sensor connection line. Therefore, it is first necessary to check whether the sensor connection line is normal, such as whether the line is open, short circuit and other problems. If there is a problem with the line, it needs to be repaired in time.

2. Replace the sensor

If the inspection finds that the sensor connection is normal, then the crankshaft position sensor may need to be replaced. Replace the sensor correctly according to the model and maintenance manual. When replacing a sensor, pay attention to the sensor specifications and models to ensure that the new sensor matches the vehicle.

3. Check the engine control system

Crankshaft position sensor failure can also be caused by a problem with the engine control system. Therefore, after checking the sensor itself and the connection line, it is also necessary to check whether there is a problem with the engine control system. If there is a problem with the engine control system, it needs to be repaired or replaced in a timely manner.

4. Check vehicle maintenance history

Sometimes the crankshaft position sensor failure can be caused by incomplete or faulty vehicle maintenance history. For example, some service operations may cause damage to the sensor or change the sensor's parameter Settings. Therefore, when troubleshooting, it is necessary to carefully check the vehicle maintenance history to understand the previous maintenance and operation.

B. Preventive measures for crankshaft position sensor failure

1. Check the sensor connection line and engine control system regularly

In order to prevent crankshaft position sensor failure, the owner should regularly check the sensor connection wiring and engine control system. Especially after driving a certain distance, it is necessary to check whether the connection line of the sensor has aging, wear and other phenomena, and repair or replace the relevant parts in time.

2. Proper use and maintenance of the vehicle

Owners should use and maintain their vehicles properly and avoid driving in extreme environments. In addition, the owner also needs to maintain and replace parts in accordance with the requirements of the repair manual to ensure that the vehicle is always in good working condition.

3. Repair the faulty parts in time

If the vehicle has a crankshaft position sensor failure or other related parts failure, the owner should send the vehicle for repair in time to avoid the expansion of the problem leading to more serious consequences. In the maintenance process, the owner should choose a regular maintenance factory and professional technicians for maintenance to ensure the quality and safety of maintenance.

C.Sensor Replacement Process

1. Find the crankshaft position sensor: First you need to find the position of the crankshaft position sensor. It is usually mounted on the front or side of the engine assembly and is relatively easy to spot. If you are unsure, check the vehicle's owner's manual or consult a professional technician.
2. Power off: Before replacing the sensor, first disconnect the power supply to avoid any accidents. Locate your car's battery and remove the negative using a wrench. Keep in mind that when the power is disconnected, some vehicle Settings, such as car stereo and radio Settings, may be lost.
3. Remove the original crankshaft position sensor: Once you have found the sensor, you need to remove it. It is usually necessary to use a screwdriver or wrench to tighten or loosen the sensor clockwise or counterclockwise.
4. Install new crankshaft position sensor: Once the original sensor is removed, the new sensor can be installed to the same position. Make sure the new sensor is properly installed and then tightened with a screwdriver or wrench.
5. Post-test: Reattach the battery and start the car and let the car run for a few minutes to make sure the sensor works the way you set it up. If all is well, resume operations and be ready to drive!

Note:

Please note that some cars require the use of specialized equipment to replace the crankshaft position sensor, so if you are unsure how to do so, you should contact a professional technician to help you replace the crankshaft position sensor. The cost of replacing a crankshaft position sensor can vary widely, depending on the make and model of the vehicle, the specific price of the part, and labor costs. On average, you can expect the total cost to range from around $120 to $300. This includes both the cost of the new part, which can range from $20 to $100 or more, and the cost of labor, which can range from $100 to $200. Please note that these are rough estimates and the actual cost can vary. It's always a good idea to get a quote from a trusted mechanic or auto repair shop for the most accurate estimate.