andyschiu

This problem just started to pop up. Sometimes when I start the car and I am driving, the speedometer does not work; it just sits at "0". Then all of a sudden it will jump to the mph driving speed I am at.

Sometimes when I start the car and drive the speedometer works fine.

Any ideas what could be the problem? Thanks.

tomgadgets

This is absolutely "normal" for our old LS400. I have a 93 as well and the speedo AND tach needles stay at zero until when I hit a pothole and it will jump back to life. You can try hitting the dash on top of the instrument panel and it will sometimes wake up the needles. This is caused by a "stuck" needle and does not affect the odometer or anything else. You can have the instrument panel service, fix the backlight issue + stuck speedo/tach needles all at once. It is not an expensive repair, I think just lube up some of the mechanism and that's it, plus some caps for the backlight.

andyschiu

Thanks. I will try hitting the dash next time it gets stuck and see how that works. Somewhat good to know that it's common on the car, but wish it wasn't a common problem so to speak. lol.

nemisonic

there are two speed sensors on the LS400/SC400 transmission. One is for the ECU to determine shift points, the other runs the speedo and tells the ECU shift points. Get the service manual (it's on this forum as a download). Or just have a shop replace the two speedo sensors.

//hitting the dash is stupid, it is a solid state dash that receives electronic signal, not a spinning cable like GM's

tomgadgets

Nemisonic,

Hitting the dash ABSOLUTELY fixes the stuck needle issue in 93-94 LS400 temporarily, until you turn off the ignition. It is a mechanical issue, NOT a sensor issue. The solid state dash still has to spin a MECHANICAL needle. It is this MECHANICAL NEEDLE that is stuck.

Please browse the forum and you will see that hitting the dash will indeed fix a 93-94 LS400 stuck speedo/tach needle issue. It has been reported by numerous forum members. It is indeed a stupid fix, but it is better than not having any speed indication at all.

python

iTrader: (4)

bad knowledge

andyschiu

Tried hitting the dash today when the tachometer and speedometer were stuck. The tachometer started working but no luck on the speedometer. lol

tomgadgets

Andy, I have the opposite effect when hitting the dash. My speedo works but the tach needle stays stuck, unless I hit it again a couple times. At least you find a way to "unstuck" your needle. Good luck.

andyschiu

Ok, I had to hit the dash above the speedometer about 10 times until it started working. Had to do it on the way to work and also on the way back from work. lol