As the name implies, a crankshaft position sensor measures the position of the crankshaft and its rotational speed (revolutions per minute). This data is sent to the engine control unit (ECU) and used to determine engine processes such as timing and fuel injection.
As you would expect, the signal wire with the information about the crankshaft’s position and RPM connects directly to the ECU. For a 3-wire crankshaft position sensor, two additional wires also connect to the ECU.
Let’s dive in for detailed information about the 3-wire crankshaft position sensor diagram and how to test it using a digital multimeter.
3-Wire Crankshaft Position Sensor Wiring Diagram
The first task would be determining whether your car has a 2- or 3-wire crankshaft position sensor. That depends on the type of sensor it has.
Two main crankshaft position sensor types exist; inductive or magnetic pick-up and Hall Effect. The main difference is their operation principle and the number of wires connected to them.
An inductive or magnetic pick-up crankshaft position sensor has two wires and does not require reference voltage. It generates its voltage, which is the signal sent to ECU for interpretation to determine the position and RPM of the crankshaft.
On the other hand, a Hall Effect sensor has three wires. That is because it has an additional circuitry that requires power to amplify the signal before sending it to the ECU.
With that said, let’s get into the 3-wire crankshaft position sensor wiring diagram. As you know, this sensor type has three wires connected to the ECU. They are as follows:
- Reference voltage wire– This wire comes from the ECU and has a reference voltage of 5V in many cases but can also be 12V, depending on your car’s make and model.
- Signal wire– comes from the sensor to the ECU. The wire has a digital signal with information about the position and RPM of the crankshaft.
- Ground wire– this wire also connects ECU and the sensor. It completes the circuit by offering a return path for the current from the sensor’s internal circuitry.
So, what does a 3-wire crankshaft diagram look like? It is not hard to guess because everything is pretty straightforward. In fact, you can trace every single wire from the sensor back to the ECU when troubleshooting wiring problems.
All three wires from the crankshaft position sensor connect it to the ECU. As mentioned, the sensor needs a power supply. This comes from the ECU and can be 5V or 12V. On the other hand, a return wire, commonly known as the ground, connects the sensor to the ECU.
Lastly, the third wire is the signal wire. This transfers the sensor’s output to the ECU for interpretation. The wiring diagram can be visualized as shown below:
How To Test a 3-Wire Crankshaft Position Sensor with a Digital Multimeter
Symptoms of a faulty or malfunctioning crankshaft position sensor overlap with other car components. As a result, you cannot be sure if it is the culprit without testing it. Even using an OBD2 scanner to read the fault code cannot accurately pinpoint the actual cause. The check engine light can be triggered by a wiring problem.
The best way to determine whether or not a crank sensor is faulty is by testing it using a digital multimeter. Set the meter to DC voltage and measure the readings on the signal, reference, and ground wires. Compare these with the nominal values stated in the car repair manual.
But how do you actually carry out the test? It is more complicated than just hooking a multimeter to the sensor. Proceed as follows:
- Check and identify all three wires from the crank sensor. Refer to the car’s user manual to use color codes to distinguish the wires.
- Turn on the ignition without starting the engine and hook the multimeter across the sensors. Connect the red probe to the reference wire and the black one to the ground wire and set it to DC voltage. The reading should be about 5V or 12V, depending on your car’s make and model.
- Start the engine and transfer the red probe from the reference voltage to the signal wire. The multimeter should show a reading of about 5V. Zero or inconsistent reading indicates a faulty crank sensor.
- Test the continuity of the ground wire. This will help eliminate it as the culprit if the signal reading is inconsistent.
Alternatively, you can conduct a resistance test on the crankshaft position sensor. Set the multimeter to ohms and connect its leads across the reference and ground wire when the ignition is off. You should get a reading of about 200-1000 ohms. Refer to your car repair manual for the expected resistance value.
How can you tell if a crankshaft sensor is bad?
A faulty crank sensor is associated with the following symptoms:
- Hard starts
- Engine stalls suddenly
- Illuminated check engine light
- Frequent misfires
- Violent engine vibrations
- Rough idle
- Reduced fuel economy
Why should the 3-wire crankshaft position sensors need a reference voltage?
3-wire crank sensors have circuitry that needs the power to function and generate signal voltage. A reference voltage is, therefore, required for it to work. This can be 5V or 12V, depending on the make and model of the car.
How can you test a crankshaft position sensor?
You can test the crankshaft position sensor in your garage if you have a digital multimeter. This is quickly done by measuring the sensor’s resistance and comparing it with the value provided in the car repair manual. A significant difference shows a fault in the device.
How much resistance should a crankshaft sensor have?
A properly functioning crankshaft sensor should have a resistance of between 200 ohms and 2,000 ohms. This depends on the car’s make and model. Refer to your car’s repair manual for the expected value.
What sensor failures can cause a crank no-start?
The engine start is a complicated process in modern cars. Multiple sensors and components must work together to aid it, and these include the following:
- Crankshaft position sensor
- Throttle position sensor
- Coolant sensor
- Fuel pump
A wiring problem or failure of these sensors and components will cause a crank no-start.
3-wire crankshaft sensors with 5V reference voltage are the most common compared to 2-wire sensors. That is because they are more accurate and reliable. And because of the three wires, they are connected differently to the ECU. Also, they have a different working principle.
All three wires from a 3-wire crank sensor connect to the ECU. They include wires with a reference voltage, signal, and return wire, all of which should be well connected for the proper functioning of the sensor.