MattLS400

Members,
I would be grateful for an explanation as to why my 1996 Celsior( UCF21) speed -o-meter and odo-meter are not working on my instrument cluster. BUT my tach-o-meter, temperature gauge, fuel gauge and all other warning lights are working perfectly.

My guess, is that my speed sensor is not working. Can I have a location and a number for this part ? Thanks

dengman

what year?

sha4000

iTrader: (1)

I think if you sensor was faulty it would definitely throw a code. Search the forum for the Speedo/instrument cluster fix since that is a known issue Matt.

steve2006

As mentioned in the question 1996

steve2006

Cluster fix on the 1996 model year? 1992-1994 yes but on the series III not come across a problem with them.

steve2006

There are 2 speed sensors mounted on the driver's side transmission near the top, IIRC one is for the speedometer the other provides information to the transmission ECU.
According to the exploded diagram they are both the same part numbers (89411-50010) priced at around $120.00 each.
I would check the wiring to them and the plug and socket connections first.

timmy0tool

iTrader: (7)

yes, i would think a bad speed sensor would throw a CEL. could this be related to bad capacitors in the ECU? (awaiting cowboy's response).

LScowboyLS

speed sensor is not a part that tends to go bad on LS400, although it sure gets suspected a lot!

the speedometer not working could be cluster capacitors, ECU capacitors (including being rebuilt with incorrect ones) or a mechanical sticking problem (lubricant becomes old and sticky)

it can be difficult to ascertain which of these is the culprit, without just plain old trial & error

sha4000

iTrader: (1)

My speedo light is out and it sticks every now and then.

MattLS400

I should make it clear that my needle has never moved since I got the car...therefore, its not "sticky" ...its just dead...

Yamae

Don't conclude without confirming the detail. Things are not always that simple. You'd better to check the signal named SPDM (pin8 of connector B at the meter unit or pin12 of connector E at the ECU) first. The color of the wire used for the line is yellow. Can you observe any signal at here?

The signal SPDM stands for SPeeD Meter and it is originally from the speed sensor but it is not directory sent to the speed meter unit. It is processed by the ECU and the pre-processing interface circuit before sent to the meter unit.

An oscilloscope is the best to observe the SPDM signal but you can check it using an audio amplifier and a speaker catching it as a sound.

dashan

Hit the dashboard really hard several times with your hand while you are driving at 20-30 mph. That might wake up the needle.

LScowboyLS

I am still of the opinion that Matt's ECU is not correctly repaired, I would like him to post high resolution photos of the bottom ECU circuit board, so that we can verify that the correct type of capacitors were used and they were installed correctly.

MattLS400

Thanks steve !

zyzygy

Before fixing the caps on my 96, when the car was fueled up it only marked 3/4 full, after the fix it went up to 4/4; no more issues after that