How to Test a Vehicle Speed Sensor with a Multimeter

Ementes Technologies
Ementes Technologies

A vehicle speed sensor, or VSS, is a sensor that measures how fast your vehicle is moving. If your vehicle’s speedometer stops working or isn’t displaying the correct speed, you most likely have a faulty VSS. A multimeter can be used to test your VSS to ensure that it is working properly. Begin by disconnecting and removing the VSS from your engine so that it can be tested. After that, connect it to a multimeter and set it to the AC setting. Connect the VSS to a power drill to simulate the rotation of the vehicle’s transmission and use a multimeter to see if the voltage increases as the speed increases to determine if the sensor is working properly.

Part 1 Disconnecting the VSS

1. To avoid being shocked, make sure the vehicle is turned off. Place the vehicle in park on level ground and turn off any lights or accessories that may use battery power. Remove the key from the ignition to ensure that the engine is completely turned off.

Parking on flat ground makes it easier to get to the VSS.

2. Open the vehicle’s hood to gain access to the engine. To open the hood, locate and pull the release hatch near the driver’s side door. Raise the hood by engaging the interior release hatch on the front of the hood. If your hood is held open by a rod, return the rod to its slot.

Before you lean into it to test the VSS, make sure the hood is securely fastened.

3. Locate your vehicle’s VSS sensor near the transmission. Locate the transmission dipstick and use it to find your transmission. The VSS is a small sensor that is wired to your transmission and held in place by a bracket. It will also include a sliding pull tab. Look for a small metal sensor surrounded by a metal bracket and connected to a white and black wire.

Vehicle speed sensors can be installed in a variety of locations depending on the make and model of your vehicle, but because they measure the rotation of the transmission, they are usually installed on or near the transmission.

To find the location of your VSS, consult your owner’s manual.

Tip: If you don’t have your owner’s manual or are unable to locate your vehicle’s VSS, search the make and model of your vehicle online.

4. Disconnect the VSS’s wiring harness connector. The VSS is wired with two wires, one black and one white. Both wires connect the VSS to your vehicle, grounding the sensor and transmitting speed information. Unplug the harness so that you can remove the sensor.

The wiring harness could be found on the VSS’s underside.

If you can’t grip the harness with your fingers, disengage it with a pair of needle-nose pliers.

5. To separate the VSS, pull the tab or press the button. A sliding tab or a button will be located on the top or side of your VSS. Engage the tab or button and gently pull the sensor away from the housing.

The VSS may need to be wiggled or slid out of its base.

Don’t yank or force the VSS or you’ll damage it. Check that the sliding tab or the button that releases it is engaged.

To slide some sensors out of place, you may need to remove two small screws.

6. To remove the VSS, unscrew the hold-down bolt and bracket from the VSS. To remove the bracket that surrounds the VSS, use a screwdriver. To remove the sensor, you’ll need to twist the bolt with a socket wrench that has a piece that fits over the bolt and loosen it enough to pull it out.

Make certain that none of the screws or bolts are lost so that you can replace the sensor.

Part 2 Connecting the Multimeter

1. Connect the coloured lead cables to the multimeter’s lead cable slots using the coloured lead cables. A red and a black lead cable will be attached to your multimeter. Connect the black lead to the terminal labelled “COM,” which is an abbreviation for “common,” which is also black in colour. Afterwards, connect the red lead to the red-colored terminal labelled “V” for voltage, which is what you’re looking for to test.

Completely insert the leads into their respective slots. When they’re fully connected, they may “click” into place as if by magic.

2. To check your VSS, switch the multimeter to the AC setting. Look for a dial on your multimeter that has both numbers and letters written on it (see illustration). The AC, or alternating current, setting is denoted by the letters AC, V with a squiggly line, or ACV on the control panel. Turn the dial until the arrow or indicating line is pointing in the direction of the A/C setting (see illustration).

Electrical devices, such as your VSS, are powered by alternating current (AC).

3. Connect a signal output wire as well as a ground wire to the sensor. On the VSS, there is a slot into which the sensor can be plugged in to the vehicle. From auto supply stores, you can purchase a plug that fits into your VSS and contains a white signal output wire and a black ground wire for your VSS. Check to see that the plug is securely attached to your VSS.

When transmitting signals from the device to your vehicle, the plug makes use of a white signal output wire and a black ground wire to do so.

On the internet, you can also find plugs that contain both the signal wire and the ground wire.

4. Connect the black and red leads to the corresponding wires on the plug. To connect your black lead wire to the exposed wire at the end of the black ground wire that is plugged into the VSS, clip it together. To complete the circuit, connect the exposed end of the white signal wire that was previously connected to the sensor with your red lead wire.

Check to see that the red and black leads are securely connected together.

Using a knife, cut through the sheathing on the signal wire and ground wire to expose the wire beneath, which will allow you to clip your leads to it. If the signal wire and ground are completely covered in sheathing, cut through the sheathing on the signal wire and ground wire.

Part 3 Rotating the Sensor

1. Find a drill bit that will fit snugly into the VSS and use it. To properly test the sensor, you must rotate the gear inside the VSS in order to simulate the movement of your vehicle and properly test the sensor. Drill drill bits into the gear slot on the VSS until you find one that fits snugly into the slot and is secure.

Several different sensors have a variety of slot sizes, so experiment with a few different bits until you find one that fits your VSS.

2. Connect the drill bit to the power drill’s chuck. To loosen the chuck, or the piece at the end of the drill, rotate it until the jaws of the chuck open up. The smooth end of the bit should be inserted into the jaws first, and then the drill should be slowly rotated to tighten the jaws around the bit so that it is securely held in place.

Pulling on the bit with a gentle tug will ensure that it does not fall out.

3. Pulling the trigger on the drill causes the VSS’s gears to turn. The VSS should be held firmly in place with your hand while you slowly speed up the drill to rotate the gears in a slot that the drill bit has been inserted into. Allow the VSS to rotate at its maximum speed in order to obtain an accurate reading.

Start slowly and gradually increase the speed of the drill while maintaining a consistent pace to avoid stripping or damaging the VSS.

4. Check the voltage on the multimeter to see if it increases as the speed of the vehicle increases. The voltage reading on the multimeter will be displayed while the VSS is rotating. If the VSS is operating properly, the voltage displayed on the multimeter will increase in proportion to the increase in the speed of the VSS rotation.

If the voltage does not increase or if the display does not appear at all, the VSS is damaged or defective.

Consider rotating the VSS at different speeds to ensure that the multimeter is accurately detecting changes in speed.

5. The VSS should be reinstalled into your vehicle after the plug and drill are disconnected. Remove the drill bit from the VSS and pull out the plug that contains the white signal output wires and the black ground wires, as shown in the picture. If the VSS is in proper working order, slide it back into its housing, reconnect the wiring harness, and replace the bracket and bolts as necessary.

If your VSS is not functioning properly, it should be replaced with one of the same make and model so that it will fit into your vehicle.

If your vehicle’s vehicle stability system (VSS) is operational but the speedometer is not, have a mechanic inspect your vehicle.

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