How to test a 3-wire pressure sensor?
By the end of this article, you will know how to test a three-wire pressure sensor.
Testing a 3-wire pressure sensor can be tricky. In the end, you will have to check all three wires for voltage. These wires have different voltages. So, without proper understanding and execution, you can get lost, which is why I'm here to help!
In general, to test a 3-wire pressure sensor:
- Set the multimeter to voltage measurement mode.
- Connect the black lead of the multimeter to the negative battery terminal.
- Connect the red probe of the multimeter to the positive terminal of the battery and check the voltage (12-13 V).
- Turn the ignition key to the ON position (do not start the engine).
- Find the pressure sensor.
- Now check the three connectors of the three-wire sensor with the red multimeter probe and record the readings.
- One slot should show 5V and the other should show 0.5V or slightly higher. The last slot should show 0V.
For a more detailed explanation, follow the post below.
Before we begin
Before proceeding to the practical part, there are a few things you should be aware of.
Understanding the three wires in a pressure sensor can help you a lot when testing the sensor. So let's start with this.
Among the three wires, one wire is the reference wire and the other is the signal wire. The last one is the ground wire. Each of these wires has a different voltage. Here are some details about their voltages.
- The ground wire must be 0V.
- The reference wire must have 5V.
- If the engine is off, the signal wire should be 0.5V or slightly higher.
When the engine is turned on, the signal wire shows a significant voltage (5 and below). But I'm going to do this test without starting the engine. This means that the voltage should be 0.5 V. It may rise a little.
Tip of the day: The pressure sensor wires come in different color combinations. There is no exact color code for these sensor wires.
What is Reverse Probing?
The technique we use in this testing process is called reverse probing.
Checking the current of a device without disconnecting it from the connector is called reverse probing. This is a great way to test the voltage drop of a pressure sensor under load.
In this demo, I will walk you through how to test a 3-wire automotive pressure sensor. The car comes with various types of pressure sensors, such as air pressure sensors, tire pressure sensors, absolute pressure sensors, fuel rail sensors, etc. For example, an air pressure sensor detects atmospheric pressure.(XNUMX)
7-Step Guide to Testing a 3-Wire Pressure Sensor
The fuel rail sensor monitors fuel pressure. This sensor is located in an easily accessible location in your vehicle. So this 3-wire sensor is the perfect choice for this guide. (2)
Step 1 - Set your multimeter to voltage mode
First, set the multimeter to constant voltage mode. Rotate the dial to the appropriate position. Some multimeters have autorange capability and some do not. If so, set the span to 20V.
Step 2 - Connect the black wire
Then connect the black lead of the multimeter to the negative terminal of the battery. The black wire must remain on the negative terminal until this test is completed. You can use this connection as a ground for this test.
Step 3 - Check the ground
Then connect the red lead of the multimeter to the positive battery terminal and check the reading.
Readings should be above 12-13V. This is a great way to check grounding. You can also check the status of the power supply with this step.
Step 4 - Locate the 3-wire sensor
The fuel rail sensor is located in front of the fuel rail.
Step 5 - Turn the ignition key to the ON position
Now get into the car and turn the ignition key to the ON position. Remember, do not start the engine.
Step 6 - Check the three wires
Because you used the reverse probing method, you cannot unplug the wires from the connector. There should be three slots on the back of the sensor. These slots represent the reference, signal, and ground wires. Thus, you can connect a multimeter wire to them.
- Take the red lead of the multimeter and connect it to the 1st connector.
- Write down the multimeter readings.
- Do the same for the other two remaining slots.
Use a paper clip or safety pin when connecting the red wire to the three slots. Make sure the paperclip or pin is conductive.
Step 7 - Examine the readings
You should now have three readings in your notebook. If the sensor is working properly, you will get the following voltage readings.
- One reading should be 5V.
- One reading should be 0.5V.
- One reading should be 0V.
The 5V slot is connected to the reference wire. The 0.5V connector connects to the signal wire and the 0V connector connects to the ground wire.
Thus, a good three-wire pressure sensor should give the above readings. If this does not happen, you are dealing with a faulty sensor.
Take a look at some of our articles below.
- How to check battery discharge with a multimeter
- How to check the power supply of a PC with a multimeter
Recommendations
(1) atmospheric pressure - https://www.nationalgeographic.org/
encyclopedia/atmospheric pressure/
(2) fuel – https://www.sciencedirect.com/journal/fuel
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