Speedometer not working

[garync1]

My mother has a 1991 custom LeSabre. I have put a water pump and alt and a new belt over the years with no problem..Now her Speedo is not working and I cant find a speedo cable.. Does anyone no if it has a sensor or if there is a cable I am not finding. If so where is the VSS or cable located?? Thanks for any help.. Gary..

[chris_eitniear]

It appears that it has a VSS, at least partsamerica shows one for it. As to where its located, I really don't know. If you don't have one, you might get a Haynes manual for the car, usually available at parts stores.

[garync1]

Yea I may have to that.. This car still looks brand new. Only thing I have done is changed alternator,belt,water pump and fluids..77,000 miles. Mom does not go much.. Thanks,gary

[HotZ28]

A good way to test the VSS, is with a live data scanner that reads MPH. If the scanner will read the MPH, the VSS & ECM are OK, and the IC display may need repair.

[garync1]

Originally Posted by HotZ28

A good way to test the VSS, is with a live data scanner that reads MPH. If the scanner will read the MPH, the VSS & ECM are OK, and the IC display may need repair.

Yes i have one of those. But mine only works with 96 and above.
I may just get the book for the thing.. My mom plans on keeping it for a while.Well she said tell it falls apart. But that mean the car will out last her.LOL

[Smith1000]

I tested the VSS on my '97 Lesabre years ago. You can do it with a digital voltmeter as well. The VSS, from what I recall, has a magnetic tip that generates its own voltage within a certain range. The voltage is variable with speed and provides an input for the ECU. The ECU then provides the signal to the dash gauge. I want to say the range is 0 to 1 volt (not exactly sure, it may be less than that). Regardelss, if voltage is being produced, and you can see it move from 0, then the VSS is doing its job and the speedometer should be producing some reading.

I tapped into the signal wire with a straight pin and an alligator clip. I taped the volt meter to the winshield (outside), so that I could read it through the windshield. You then have to drive around and watch the output.

If it is producing voltage, next the voltage can be checked going in and out of the ECU. Also, it could be checked at the gauge as an input. This rules out a problem at the ESU or with the wiring. That part is likely okay. It may just be in the cluster. For my 97, the speed was reading erratic. Also, the tach was jumping. It had a bad cluster. I found a salvaged one and that did the job. Good luck.

[garync1]

Thanks.. I just want to find the thing now. I hope if I spend the money on the book it will help me locate it.

[BNaylor]

Originally Posted by garync1

Thanks.. I just want to find the thing now.

You should have the TH440T4 autotransaxle, GM RPO code ME9 and later dubbed the 4T60. GM typically installs the VSS on the right (passenger side) transaxle extension housing where you see the right axle shaft and the differential. You should see a lone wiring harness going to the sensor in that area.

I don't recall the exact type VSS used but the ones for later GM models normally output an AC voltage of around .4-.5 volts as you spin the passenger side wheel in neutral and of course jacked up.

[garync1]

Thanks BNaylor. From what i look at today you just help me. I think i know what you are typing at.. I thank you.. Just did not wont to get the book and it not be in there. Some books dont show them. Not sure if haynes did. This will help. I did pull the plug on that one and others just to check to see if they were clean. They were fine so i will check out with volt meter tomorrow. I will post results. I also did not wont to replace a pricey part like that one is with out knowing. So far about 68.00 was the cheapest and 90.00 was the highest. THANKS!! Gary

[Smith1000]

You might check the public library for the detailed technical book info. That's what I used to do before the Internet. Still do use the automotive manuals at the library occasionally. It might be better than buying the book and finding out it really doesn't have what you want.

[garync1]

Ok changed the Speed sensor and it did not work at first. So i pulled the dash and clean the cluster copper strips on both speedometer unit and factory harness. Put cluster back in did not work. Well after putting everything back together. Took for another drive and it works. Then retested did not work. Drove one more round and it works. After more testing I notice it works better when the heat or AC is on. So may have a short some where. opcorn: So will see how it works out. Thanks for the help..

[rick444]

I have a 90 lesabre, no speedometer reading. Cruise works. I suppose that means the problem is at the cluster.
Did you find your exact cause?
Thanks.

[jcc3inc]

Sir,

We have a '97 with speedo and tach. The speedometer became intermittent, and after some fooling with it, I took it out and found an intermittent open on the circuit board. Resoldering it made the speedometer and odometer work again.

Regards,
Jack C.