Ali SC3

iTrader: (10)

trust me, just swap that board out unless you are very good with electronics.
the motors are delicate, dont turn the motor at all when the needle is not attached as this will lead to the problem you are trying to fix.

basically dissasemble both clusters down side by side to the point where you can swap out the boards then remove the bad one first and set it aside. now remove the good one and swap it to the other cluster, reassemble .

Li Ls4

iTrader: (12)

thanks for the help Ali, now I just need to find myself a cheap working cluster haha

zukikat

Hey Ali SC3,

I've got an odd SC400 speedo problem puzzle for 'ya.

The odometer counts normally with the miles that are showing as getting added to it being proper for the distance driven, BUT at very low speeds the speedo needle suddenly leaps to life and begins "bouncing" between 0 and about 15mph then as you slowly go faster the range of the needle bounce gets smaller with the needle favoring 0mph, then by about 10mph (actual speed of the car by my gps) the bounce has stopped and needle stays on the 0 peg.
Then on decel as you're approaching a stop the needle starts that same bouncing again and then finally settles on 0 shortly before the car comes to a complete stop.
Sometimes though if you get the car stopped in the middle of the needle bounce the needle stops wherever it was at that moment instead of falling to 0.
It's like it's misinterpreting the pulses from the sensor?

I don't have a scope to check the actual sensor signal but aren't the speedo and odo driven off the same sensor? I haven't had a chance to really go through the schematics but I didn't notice a separate sensor feed for speedo and odo, did I miss something?

The pin-outs and wires for the sensor to speedo path are the same on both years according to the two factory wiring books and the odo works fine so I don't know what to think of this wierd speedo behavior other than a bad speedo but noone else has described anything like this online at all that I can find???

I'm 99% certain it's a 96 tranny/sensors/etc in the 93 car but if it was an issue of some sort of difference between the two years then I'd expect the odometer to also be misbehaving? I'd like to swap the cluster and see what happens but there aren't any clusters in the junkyards around here and I don't know if there are compatibility issues with certain years or if they're all basically interchangeable?

***A little background, just in case...

A friend bought this 93 SC400 with a 96 tranny/engine/engine-harness/ecu combo dropped in but not finished, wouldn't start, no spark and no fuel and the seller couldn't figure out why.

I finished connecting all the engine harness wiring plugs to the body, determined that the remaining "extra" connectors in the 96 engine harness are for TRAC which this particular 93 chassis doesn't have, and then added an OBD-II diagnostic data link connector to the car so I could use my OBD-II reader on this 96 ECU, which revealed that we were getting the P1300 and P1305 Igniter Circuit #1 and #2 Malfunction codes that I easily solved using both the 93 and 96 factory Lexus SC wiring books and got the engine to fire right up with a normal turn of the key.

I also fixed the bizarre 93/96 "oil level" and "abs" warning lamp swapped wires issue and verified every pin of all involved 93/96 connectors and the car now "runs and drives" as expected with no more OBD-II codes being reported even after we drove it about 30 miles yesterday.

zukikat

Well the next time we drove the car the wobble got a little less and this time it stabalized and stopped dropping to zero as we increased speed, although the speed it shows while driving is nowhere near correct at this time, even on the stock tire size. This time the speedo said we were doing maybe 25mph at 40mph and I think it hit 50 or maybe more while we were on the interstate going much faster than that but that's a huge improvement over its' behavior as listed above when we drove the car for the first time after I finally got it running.

The cruise control actually works on both city streets and on the interstate and the odometer counting seems accurate so I suspect a cluster/gauge problem at this point and I'm hoping it eventually figures itself out.
It would also seem that this cluster might not be original to this car as the backlighting color doesn't seem correct for the year from what I've read, plus the airbag warning light was constantly lit and it finally went out like it should be after I did the "airbag light reset" procedure so its' being constantly on when we got the car tells me the instrument cluster has been disconnected from the car at some point in the past by the previous owner.

Just thought I'd give an update...