Modern cars are complex machines that require precise synchronization of various components to function optimally. The crank position sensor is one such component that plays a critical role in ensuring the engine runs smoothly. In this guide, we will discuss what a crank position sensor is and its purpose in a car. We will also talk about the symptoms of a faulty crank position sensor and what you can do to troubleshoot the issue. 

What is a Crank Position Sensor?

A crank position sensor is an electronic device that measures the rotation of the crankshaft in an engine. It detects the exact position of the crankshaft and relays this information to the engine control module (ECM), which is the computer that controls various functions of the engine.

The crank position sensor is usually located near the crankshaft, either at the front or rear of the engine, depending on the design of the vehicle. It can be a magnetic or a hall-effect sensor and can be in the form of a wheel or a disc with teeth or slots.

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Purpose of a Crank Position Sensor

The main purpose of the crank position sensor is to provide the ECM with information about the position of the crankshaft. This information is essential for the ECM to control various aspects of the engine, such as fuel injection timing, ignition timing, and engine speed.

Fuel Injection Timing

The fuel injection system is responsible for delivering fuel to the engine cylinders at the right time and in the right amount. The crank position sensor provides the ECM with the position of the crankshaft, which enables the ECM to determine when each cylinder is ready to receive fuel. This information is crucial in ensuring that the fuel is injected at the correct time, resulting in optimal engine performance.

Ignition Timing

With the fuel delivered to the cylinder, the engine now needs to know when to apply spark. The crank position sensor provides the ECM with information about the position of the crankshaft, which allows the ECM to precisely deliver spark when and where necessary. Keep in mind that the ECM uses both the crankshaft position sensor and the camshaft position sensor for this purpose. This information is essential in ensuring that the spark is generated at the correct time, resulting in optimal engine performance.

Engine Speed

The crank position sensor also provides the ECM with information about the speed of the engine. This information is essential in controlling various functions of the engine, such as idle speed, and ensuring that the engine operates within the specified range.

Troubleshooting the Crank Position Sensor

When a vehicle’s engine is not running correctly, one of the components that could be causing the problem is the crank position sensor. Here are some common symptoms of a faulty crank position sensor:

Engine Misfires or Stalls

Since the ECM relies on the information provided by the crank position sensor to control fuel injection and ignition timing, a faulty sensor may cause the engine to misfire or stall.

Difficulty Starting the Engine

If the ECM does not receive accurate information from the crank position sensor, it may prevent the engine from starting altogether.

Rough Idling

The ECM uses the crank position sensor data to control the engine’s idle speed. If the sensor is faulty, the engine may idle roughly or even stall.

If any of these symptoms are present, it’s important to troubleshoot the crank position sensor to determine if it’s the cause of the issue. Here are the steps to take:

Check for Error Codes

When a problem arises in the engine management system, it often triggers an error code that can be read using an OBD-II scanner. The scanner will provide a code number that corresponds to a specific problem, and in some cases, it may even indicate which component is causing the issue.

If the scanner reads a code related to the crank position sensor, it’s essential to note the code number for reference during troubleshooting. Here are some of the more common codes related to the crankshaft position sensor. 

• P0336: Crankshaft Position Sensor A Circuit Range.
• P0337: Crankshaft Position Sensor A Low Circuit Input.
• P0338: Crankshaft Position Sensor A High Circuit Input.
• P0339: Crankshaft Position Sensor A Intermittent Circuit.

Inspect the Sensor

If there are no error codes related to the crank position sensor, the next step is to inspect the sensor visually. Look for signs of damage or corrosion, and ensure that the wiring connections are secure.

It’s worth noting that some crank position sensors are located in hard-to-reach places, and accessing them may require removing other components. If this is the case, it’s best to refer to the vehicle’s service manual for instructions.

Check the Sensor’s Output

Using a digital multimeter, check the sensor’s output voltage. The voltage should fluctuate as the engine is cranked, indicating that the sensor is detecting the position of the crankshaft accurately.

If the voltage output is outside of the manufacturer’s specifications or is not fluctuating, it’s likely that the sensor is faulty and needs to be replaced.

Check the Sensor’s Air Gap

Some crank position sensors require a specific air gap between the sensor and the reluctor wheel (the toothed wheel that rotates with the crankshaft). Check the manufacturer’s specifications to ensure that the sensor’s air gap is correct.

If the air gap is too wide or too narrow, it can cause inaccuracies in the sensor’s output, leading to engine performance issues.

Replace the Sensor

If the sensor is found to be faulty, it should be replaced with a new one that meets the manufacturer’s specifications. Installing a new sensor is a straightforward process that involves removing the old sensor and wiring in the new one.

It’s essential to follow the manufacturer’s instructions for installation, including torque specifications for any bolts or screws. Once the new sensor is installed, it’s crucial to clear any error codes using the OBD-II scanner and test the engine to ensure that the issue has been resolved.

Get Quality Crankshaft Position Sensors at Newparts.com

Troubleshooting the crank position sensor is a straightforward process that involves checking for error codes, inspecting the sensor, checking its output, checking the air gap, and replacing the sensor if necessary. The key part is using a quality crankshaft position sensor! Here at newparts.com, we offer a wide range of CPS made by some of the best brands in the industry. Head over to our store, select your vehicle and find a crankshaft position sensor that is a guaranteed fit for your car!