answersLogoWhite

0


Best Answer

HOW IT WORKS The Vehicle Speed Sensor (VSS) is a variable reluctance sensor that generates a sine wave type waveform with a frequency that is proportional to the speed of the vehicle.It has a gear on it that meshes into either the transmission/transaxle or the differential (depending on the vehicle.Probably in the differential of a Ford Ranger) When the vehicle is moving slowly, the sensor produces a low frequency signal. As the vehicle speed increases, the sensor produces a higher frequency signal. This signal is sent to the PCM and is converted into a vehicle speed value, stored in RAM memory. The PCM utilizes this value to aid in controlling torque converter lock-up/transmission/transaxle shift points, control fuel injection, ignition timing and , coolant fan control, vehicle speed control, air/fuel ratio and ignition timing. MY OBERVATIONS AND COMMENTS It works like a little alternator of sorts, or probably more correctly like the rotor and pick-up in an electronic ignition system. When it is spinning with the transmission or differential gears it generates small electric pulses which are sent to the engine control computer. The faster it spins the higher the frequency. I have tested some of mine two different ways. One way is to remove it from the tailshaft of the transmission or the differential housing (depends on vehicle)and hook the two leads to a volt meter on the AC scale or if you have a digital meter with a frequency scale you can use that too. This will measure the frequency in HERTZ (Hz.),meaning cycles per second. Spin the little gear(probably nylon)as fast as you can by hand (drag your hand /arm across it real fast like you were winding up a toy car or top)and watch the voltmeter for a reading. If you get a reading ( a few volts or Hz.) it's probably still functioning. You could also turn the gear with a variable speed drill.Keep it slow to be on the safe side.I'm guessing under 1000 RPM (most variables top out at 1250rpm for 1/2" and 2250rpm for 3/8"). If it won't go in the drill chuck (some gears have a little nub on the end you can grab),then wrap the gear with some tape and press the gear onto the side of the chuck,sort of like a bicycle generator on a bike tire.The tape will protect the little gear and help increase the friction between the two so it spins easily. Another way is to leave the sensor in place, jack up the vehicle,drive wheels off the ground and turn the drive wheels by hand with your test apparatus hooked up to the leads on the sensor for similar results. The main thing is that you get varied voltages/frequencies at different speeds.If you get nothing it's busted. I DO NOT recommend that you run the vehicle while it is jacked up. Spinning the wheels by hand will tell you all you need to know. I don't know the exact voltage or frequency you should get because it's all based on how they designed the sensor, how they calibrated the computer,the gear ratios of the sensor to the transmission or differential, and how fast you spin it. If you get different voltage and/or frequency readings at different speeds,it's probably good. The resistance across the two terminals of the sensor for a 1993 Ford RANGER is supposed to be 190 to 250 OHMS. If the sensor checks out good ,you may have a problem in the connectors or wiring .Often a close visual inspection of the connectors and wiring will reveal the problem before you have to break out a meter and run continuity checks Also check out the condition of the gear on the sensor and make sure that it is not chewed up and is properly fixed to the shaft of the sensor and not spinning loose on the shaft. I tried the first method with the drill with a 1990 Nissan speed sensor and at approx 1000 RPM I got about 7 volts AC and 270 Hz. Also, the measured resistance across the two terminals of the sensor was 258 OHMS.

User Avatar

Wiki User

โˆ™ 2006-07-30 15:08:13
This answer is:
๐Ÿ™
0
๐Ÿคจ
0
๐Ÿ˜ฎ
0
User Avatar
Study guides
๐Ÿ““
See all Study Guides
โœ๏ธ
Create a Study Guide

Add your answer:

Earn +20 pts
Q: How to check if the speed sensor is good?
Write your answer...
Submit
Related questions

How do you check if speed sensor is good Cadillac catera 2000?

If the speedometer/odometer is working, chances are the VSS (Vehicle Speed Sensor) is good.


How do you check if a wheel speed sensor is good?

You gotta smack it with your shoe.


How do you repair a code P0500 on a Plymouth Voyager?

This code indicates a problem with the vehicle speed sensor. Check the wiring and if it is good replace the vehicle speed sensor.


Speed sensor Infinity 1996 i30?

if your code is po500 check the wires between speed sensor and cluster .mostlikely your problem is in the cluster


How do you solve check engine light cause by speed sensor?

Replace the faulty speed sensor and the light will reset itself after a short drive.


Where is the transmission speed sensor on a 1995 Saturn sl?

Check


How do you check speed sensor peugeot 206?

servis control


Where can you find a schematic for the IAT sensor on a 1997 Dodge Avenger 2.0 L 5-speed?

Check out a good Public Library.


Should your speed sensor have oil on it?

I started having tons of electrical problems and they told me it was a speed sensor. I. Would suggest you check for an oil leAk.


Why the speedometer doesnt work on a 1989 astro van after replacing the speed sensor does has more than one sensor?

check for a faulty speed buffer module


ABS comes on on light braking almost stopped 2003 Chevy trailblazer?

Probably the wheel speed sensor. Check the connector. If connection is good then the sensor may have been damaged or it has failed.


What to check on a 2004 HD Road King when the turn indicators nor speedometer not check engine light do not work?

Check the speed sensor on the top of the tranny. This will tend to build up with metal shavings and cause the sensor not to read the speed of the transmission.


Where is the speed sensor located on a 1994 Saturn?

if it's like my 2002 it has a service engine code light on with a speed sensor code.it doesn't have a speed sensor, it means you need to check plugs/wires/or the electronic assy.itself.my problem was the plugs.


Why does my speedometer stop when check engine light comes on?

Possible failure of the output/vehicle speed sensor.Possible failure of the output/vehicle speed sensor.


How do you check 02 sensor if is good or bad?

If it is bad the check engine light will come on and set a code for that particular sensor.


Can a cam sensor cause a hard shift into overdrive?

yes it can but also check the speed sensor if your vehicle is equiped with one.


When the speedometer doesn't work how do you fix it?

did you check the speed sensor on the side of the transmission?


How do you check the speed sensor on a Toyota Sienna?

If your battery leak acid your speed sensor is dead. You need to replace by 89413-08020. Price average is $58.00 - $120.00 (original).


How do you find out which wheel speed sensor is gone on your 2003 Grand Am GT?

I have an 03 grand am gt, there is only one way to check out the speed sensor, bring it to a garage and have them scan it for you... this will get it correct.


Where is the speed sensor on a 06 boulavard c90 1500?

The speed sensor is located behind the right side chrome cover on the engine. Where you check your oil. It's held on by one bolt.


How do you fix error code 13 on a 1993 Jeep Grand Cherokee?

Code 13 is no vehicle speed sensor signal. Check/replace the speed sensor on the tailshaft of the transfer case.


Where is the speed sensor wire located on a 2000 infiniti i30?

The speed sensor wire is connected to the speed sensor and goes to the speed sensor relay switch. The speed sensor relay switch is connected to the computer by a separate wire.


What does check engine code P0715 mean?

Input/Turbine speed sensor malfunction


How do you replace a speed sensor on a 2004 Acura TL?

Need to know if you are asking about the vehicle speed sensor, a front wheel speed sensor or rear wheel speed sensor.


What is a free computer speed check?

A free computer speed check is a service online that offers to check the speed that your internet is providing so you can see how good of a connection you have.