MaxKechely

The title says it all, I'm just gonna list all thing things I have ruled out so far.
Checked every single fuse in the car.
Checked fuel sender assembly, giving correct readings within spec, pontentiometer is between 0 and 300ohms.
Checked fuel sender wire, + to - reading 19kohms, + to the green one reading 270ohms, and - to the green one reading something similar.
Checked fuel pump wire, got some readings, don't really know what they mean but nothings broken

Could it be the ECM, or the MAF? my mass air flow seems to be working, and same with the ECM but I don't know, my radio and map also don't work if that could be connected in some way.
Any help at all is greatly appreciated i just need someone to point me in the right direction this is driving me insane.

white_lx

The LS has a saddle tank. There are two fuel senders. Did you check both of them? Next step would be to verify voltages at the J/B.

weldthedif

Could it be the gauge cluster as well ?

MaxKechely

do you know if the one connected to the fuel pump is the main or sub one?
in order to replace that one i would probably need a whole new fuel pump container assembly
do you know where i could find the specified resistance for the other fuel sender as well?

white_lx

I'm assuming the main one is the the one close to the fuel pump. You do not need to purchase a whole pump/sender assembly. They are separate part numbers. Here is a link to the main fuel sender of an '02. (please verify your part numbers).

I would start by reading the output voltages of both senders to the J/B ECU. That verifies sensor powers, grounds and outputs in a single measurement. Or alternatively, if you have access to Techstream or another type of scanner, you can read the Fuel Gauge and Sub Fuel Gauge readings under 'meter'. That would immediately tell you if the problem is in the cluster or in a particular sensor / wiring.



Attached is a pdf with the complete inspection procedure for the fuel senders and indicator.

MaxKechely

The part number which you linked is the one which i checked, farther from the fuel pump. I will attempt to check the one connected to the fuel pump now if i can, but i don't know if it will help since it is the secondary one anyways. I may just need a new cluster?
EDIT:
nevermind the main fuel sender and secondary both look the same, I will pull out the fuel pump and check then maybe replace this one
primary:


secondary:



also If anyone knows which wires here go to the fuel sender on the fuel pump connector that would be immensely helpful

white_lx

Why don't you follow the procedure from the Lexus Repair Manual (see pdf above)? It has the complete procedure to test everything. The connector pin-outs are in the pdf as well.

MaxKechely

the manual requires an intelligent tester and i only have a multimeter
Edit again lol:
gonna have to check where those pin outs go to the ecu, thank you so much for your help

MaxKechely

Just checked my fuel pump float and its in spec, what do you guys think do i need a new cluster?

white_lx

Without actually connecting a scanner, that would be a very big guess. It could be anything from wiring to the J/B, the trunk J/B itself or the J/B powers/grounds, the wiring to the cluster or the cluster itself. You can use a $20 Techstream cable or any modern scanner to obtain the trunk J/B readings to exclude most issues except for the cluster itself.

MaxKechely

I'm sorry im new to this, but what is J/B? I have a bluetooth obd scanner can this acquire these readings?

MaxKechely

bump, still tryna find out what that means

BigBoomer

J/B = Junction Box (or at least that what I understand it to mean).

white_lx

Luggage room junction box. This is an ECU that located in the trunk. See the schematic in post #2. It takes the analog signals (voltages) of the senders and sends them through a single serial wire to the cluster, via the gateway. In the cluster, the two signals (left and right saddle contents) and displayed in the gauge.

I found the information below on diag.net. Seems to be exactly your problem. It is a paid subscription, so I don't have access to the resolution. Maybe someone else here does?

Fuel gauge shows empty, all other gauges work fine. active test fuel gauge goes from empty to half to full on demand. Sending units go from tank to the rear JB. I tested the signals at the JB both showed good, the JB sends out 4.5 volts to the sending units and returns at .01 volt, The signal voltage is the variable. showing one side at .5 v the other .3v Next step was testing from the rear JB, the signal is sent on the data lines to the Gateway and Combination Sw. I scoped out the signal MPX- into the Gateway module and the signal was there a 10v square wave the other wire MPX+ goes to the combination switch, it mirrors the signal to the gateway module. From the Gateway module it goes to the cluster. That signal mirrors the input signal. I tested the fuses that feed the cluster everything is fine.

Scan data shows fuel levels one at 30 the other at 17, probably a % number, if I ground the signal wire from the sending units to the JB the scan data changes to 6. this scan data was taken from the Instrument cluster pids.

I conclude at this point the sending units, rear JB and data signals to the Gateway module and combi sw are good, also I tested the signal leaving the gateway module to the cluster, it mirrors the input signal. the cluster knows via data lines what the fuel level is.

Is it possible to have a bad cluster even though I can control it with a scanner? One person mentioned a cluster reset, is that possible and how? I have not removed the cluster at this time/ FYI Car did have a fender bender on the left front headlight area.

MaxKechely

I would love to see the solution to this, but this stupid website requires me to be a professional mechanic in order to look at the solution for some reason. I dont understand at all why that is necessary dude.