mpatrizio

Hi guys, just got a new to me 1998 LS400.

I did a search and can't find a solution, my fuel gauge is pinned at full when the car is running. I doesn't move when I burn fuel, but when I shut the car down, the needle goes down to zero with the rest of the needles.

Does this sound like a gauge cluster problem or a sending unit issue?

Thanks in advance, this site has been a lifesaver for me!

mpatrizio

Also forgot to mention that the miles remaining calculator on the computer seems to be working properly as it is counting down.

I didn't see an issue like this anywhere in the gauge cluster thread...

ucfjon

iTrader: (1)

sounds like a gauge cluster problem right at the needle. Since you are saying that your range calculator on the computer seems to be working properly.

mpatrizio

That's what I figured, but all the failures documented in the sticky seem to have the needle either stuck on empty or slow to rise from 1/2 to 3/4 full.

I've got an email in to one of the ebay rebuild specialists.

Also, aren't the cap replacements listed in the sticky different for the '98 than the '93-'94 listed?

LexLS

That cluster sticky is just for 90-94 clusters, your 98 has a completely different circuit board. Not sure what your problem is but it does seem to lie in the cluster.

PureDrifter

iTrader: (10)

it's most likely a sender issue. iirc GrandLS4 had a similar issue. (or Kansas)

Twix

I have exactly the same issue on my 93 LS...everything works fine but the needle shows full, and when it's close to empty it is acctualy showing 1/2 of a tank...

I beleive the solution might be the same so if you find a fix, please post it...

Thanks

GRAND_LS 4

iTrader: (2)

It has been from my experience on the forums that most issues with 98+ involves sending units more then cluster issues as they were pretty much fixed in the years prior.

Mine started by not showing full after refueling, then gradually fell down to empty even with a full tank of gas. Replaced the sending unit for $60 bucks or so (did it myself. It took longer to take off the trunk carpeting then actual replacement of sensor).

This fixed the issue, as well as the Miles since refuel [reset] issue that was common on the 98's. If you plan to do this yourself, make sure you have less then half a tank, or gas will gush out when you try to remove the sensor.

WaveRunner

I'm having the same issue on my 1998 LS400. Trip computer works. Gas gauge reads full even after driving 50 miles. Gradually dropped to the middle but the low fuel light is on. Really confused as to whether this is a sender issue or instrumentation cluster issue. I purchased an OEM fuel sender to try to install myself but not sure that's the problem after reading some posts. Any advice would be greatly appreciated.

Moarpower

Replacing the sender is an easy fix and if you have the part just go ahead and do it.

WaveRunner

Thanks for your reply. I went ahead and replaced it and was disappointed to see the fuel gauge still at half even though the tank was mostly empty. Not sure what to do at this point. I'm thinking it is likely the instrumentation gauge cluster. Replacing the sender was easy except for the fact the two screws on the back of fasteners/clips on the back trunk wall/cover pulled through their respective holes rendering them useless. But all else attached so seems rigid. Not too bothered about that. I went ahead and filled my gas tank and it is showing full so will wait and see if I notice any change but I don't think the problem is fixed.

By the way, the Lexus dealer stated the problem was the fuel sender. I wonder if I had them do it what their solution would be since it wouldn't have worked. Lexus dealer wanted a whopping $850 to replace the sender. $240 for the part and the rest labor. I found a new OEM for $138 ($150 shipped) on LexusPartsNow.

Yamae

You should had measured the voltage first.
https://www.clublexus.com/forums/ls-...ml#post9850603

Now you need additional efforts to fix the cluster. It would be difficult for most of people to trace the circuits but one idea is to check the voltage regulator part of the fuel gauge circuit shown below.

Is it 5.0V at the IC's pin indicated by a red arrow? If not, replace the 5.0V regulator. If 5.0V, check soldering cracks connected traces of the pin.

I have some experience to fix many different boards of Celsiors as well as other cars requested by local shop owners and 95% of them were fixed. Most of them were not difficult for me to fix. 5% of them were caused by failed custom ICs and I had no idea to obtain those.

WaveRunner

Thanks for your reply. Unfortunately I don't have much experience with the process you stated. I am not advanced in electrical engineering. Whenever I encounter a problem I investigate and will typically try to change a faulty part myself or have a mechanic do it. As for the fuel gauge reading incorrectly, I am left to believe it is the gauge cluster since I replaced the sender and still see the same issue. My solution at this point is to either have the cluster repaired or simply get a refurbished cluster with close mileage to my car. Since my trip computer works and tells me how many miles left on my tank I am in no rush. It is strictly the fuel gauge that is out of order. I should mention my temperature gauge also reads above the half mark but no mechanic has mentioned any sign of over heating and the coolant level is fine. I'm assuming that is also tied with some fault in the cluster circuitry.

ATLs400

ever check to see if the speedo or tach are calibrated?

ATLs400

im having a similar issue. when i first got my 98 ls400(10/26/17) the dealer filled up the tank. the dte gauge was around 350ish and went down the same rate my trip meter went up. the fuel needle however didnt go down til i was about 120 miles into the tank of gas but from there it seemed to go down regularly at a normal rate. my issue now is my dte gauge has gone just saying "low fuel". last reading was around 50 miles to go. my gas light came on with the needle reading a little over a quarter of a tank. is that normal for the gas light to come on so early or do you guys think my needle is a little off?
thanks