Vehicle Speed Sensor - JeepForum.com

 
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post #1 of 6 Old 02-23-2010, 02:51 PM Thread Starter
jeeposaurus1
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1993 ZJ 
 
Join Date: Jun 2008
Location: Spring
Posts: 81
Vehicle Speed Sensor

A few days ago my speedo started acting crazy jumping all over the place while driving. Then it just quit working all together. I figured it was the vss so I started shopping around for a new one. All the parts stores have a sensor but they all require splicing wires because the plugs are different between the sensors. I decided I didn't want to cut perfectly good wires so I went to the junkyard and got one. I installed it and the speedo still doesn't work. So I have 2 questions. First, what else could have gone bad that would cause the speedo to quit, and second, is there a way to test the sensor with a multimeter to see if it is bad. It is possible that I got a bad one from the jy I suppose.


Wheeler-'93 ZJ 4.0
Daily Driver- '02 WJ 4.7 Quadradrive
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post #2 of 6 Old 02-23-2010, 02:56 PM
BigRed4x4
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1993 ZJ 
 
Join Date: Dec 2009
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Might just be the actual cluster, maybe a short or something. Try hitting the top of the dash above the cluster (not too hard) and see if anything happens.

Also I replaced my speed sensor about a year back and got the new one at the Advance Auto down the road. It went in just like the old one, no splicing.

'93 ZJ, 4.0L, D30 & D35, NP231, 4" Lift, 31" BFG's, Soft 8's, Painted Cladding, Glasspack, JVC Deck, CB, Lightbars, JKS Discos & TB, Tow Hooks Everywhere...more crap.
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post #3 of 6 Old 02-23-2010, 04:04 PM Thread Starter
jeeposaurus1
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[QUOTE=BigRed4x4;8953182]Might just be the actual cluster, maybe a short or something. Try hitting the top of the dash above the cluster (not too hard) and see if anything happens.

Yeah I thought that could be the problem but after a couple of whacks to the dash nothing changes. I'll check out Advanced and see what they have. Thanks.

Wheeler-'93 ZJ 4.0
Daily Driver- '02 WJ 4.7 Quadradrive
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post #4 of 6 Old 02-23-2010, 04:44 PM
BigRed4x4
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No problem and good luck!

'93 ZJ, 4.0L, D30 & D35, NP231, 4" Lift, 31" BFG's, Soft 8's, Painted Cladding, Glasspack, JVC Deck, CB, Lightbars, JKS Discos & TB, Tow Hooks Everywhere...more crap.
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post #5 of 6 Old 02-26-2011, 03:55 PM
Shadini
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1993 ZJ 
 
Join Date: Feb 2011
Location: Toronto
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Quote:
Originally Posted by jeeposaurus1 View Post
is there a way to test the sensor with a multimeter to see if it is bad. It is possible that I got a bad one from the jy I suppose.
It is possible you got a bad one from the wreckers, but here is how to check it using a multimeter. (Your multi-meter needs to have probes to do this!)

-NOTE: You will need another set of hands to be able to do this test.-

First off you will need to jack up one or bother of the rear wheels of the vehicle off the ground.(I did both but might have been able to do it with only one.

-NOTE:I can't stress enough that you must use a jack stand. The testing process most likely will cause a regular jack to either roll or topple over!-

Next make sure the VSS is connected to the vehicle as it would be in normal operation.

Insert the key into the ignition and turn it to the 'ON' position (Do not start the engine!)

Now head to the VSS and take a good look at it. Where you see the little plastic tab that hold the wire hardness onto the sensor will be the side I will consider as UP (It may not face up, just using it as reference.)

if the clip side is considered up, here is the info on the three wires entering the harness from left to right.

- Left wire is the sensor signal output.
- Center wire is a ground.
- Right wire is the 5v supply

What you want to do is insert the positive probe from your multi-meter into the 5v supply in the back of the harness and ground the negative probe to any suitable ground on the vehicle. If the voltage isnt around 5v, trace the wiring and search for a short. If all is well, continue to next step.

Next you need to insert the positive probe from your multi-meter into the sensor signal output in the back of the harness and ground the negative probe to any suitable ground on the vehicle.

Now get your assistant to either block one of the raised back tires so it can not move (Or hold it if you have two assistants) and rotate the other tire by hand while you watch the multi-meter's output.

The reading should fluctuate between 0 and 5 volts as the tires is rotating. If this reading is found, then the sensor is functioning properly.

If not, replace the sensor and try again.

If even after installing a brand new sensor, the test is failing, replace the speedometer pinion gear. (It is what the sensor actually connects too.)


Hope this helps, if you have any other questions please feel free to let me know.
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post #6 of 6 Old 06-03-2014, 04:25 PM
bpvideo
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7 Volt on output wire

Hate to bump an old thread but I am not having luck finding any help. My VSS output wire is showing 7 volts in! I have checked/cleaned all the grounds replaced the VSS, tried unplugging the clockspring to eliminate that. So I am down to a short I guess? It is showing 7 volts at the connector into the main harness. Any ideas or help?

1995 Cherokee 2wd AW4 Auto.
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