FUEL GAGE DOES NOT GO UP ALL THE WAY

Faulty fuel sender in the fuel tank ,poor electrical connectors on the outside of the in tank assy , faulty gauge unit at the instrument cluster . Poss auto electrician required to test circuits for open circuits and resistance.

Fuel Gage
The IPC displays the fuel level as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the fuel level percent. The fuel gage defaults to empty if:
• The PCM detects a malfunction in the fuel level sensor circuit.
• The IPC detects a loss of class 2 communications with the PCM.
When the fuel level is less than a pre-determined value, the low fuel indicator illuminates.

Hooking up a professional or factory scanner an checking input data to the PCM from the sending unit inside the fuel tank ,viewing the information sent to the IPC , Checking for diagnostic trouble code's .
DTC P0461
DTC P0462
Circuit Description
The fuel level sender changes resistance based on fuel level. The PCM monitors the signal circuit of the fuel level sender in order to determine fuel level. When the fuel tank is full, the sender resistance is high and the PCM senses a high signal voltage. When the fuel tank is empty, the sender resistance is low and the PCM senses a low signal voltage. The PCM uses the signal circuit of the fuel level sender in order to calculate the total remaining fuel percentage in the tank. The PCM sends the fuel level percent via the class 2 serial data circuit to the instrument cluster in order to control the fuel gage. The fuel level information is also used for misfire and EVAP diagnostics.

Install a scan tool.
Turn the ignition ON, with the engine OFF.
With a scan tool, observe the Fuel Tank Level Remaining parameter in the PCM data list.
Does the scan tool indicate that the Fuel Tank Level Remaining parameter is less than the specified value?
1%

No DTC'S - diagnostic trouble code's stored ,use this diagnostic procedure
Fuel Gage Inaccurate or Inoperative
• Refer to Fuel Level Specifications in order to verify the correct fuel level sensor readings. The Fuel Tank Level Remaining parameter is available in the scan tool in the PCM data list.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
This step tests for a high resistance in the signal circuit and the low reference circuit of the fuel level sensor.
DTCs will be set in the PCM when you perform this diagnostic table.
Step
Action
Value(s)
Yes
No
Schematic Reference: Instrument Cluster Schematics
1
Did you perform the Instrument Cluster Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check - Instrument Cluster
2
Disconnect C104.
Connect the J 33431-C Signal Generator and Instrument Panel Tester between the signal circuit of the fuel level sensor and the low reference circuit of the fuel level sensor on the male terminal side.
Turn the ignition ON, with the engine OFF.
Important: Verify the J 33431-C resistance settings with a DMM.
Vary the resistance on the J 33431-C from 40-250 ohms.
Refer to Fuel Level Specifications in order to convert from resistance to fuel gage display.
Does the fuel gage display the correct fuel level?

How to test fuel gauge tank sending unit P0463 GM

The fuel pump is inside gas tank behind the back seat unscrew the only top that's there and it is inside the gas tank. You will have to remove your back seat to gain access to fuel pump. Fuel tank is located in trunk. No need to take fuel tank down. Click this link for full details and procedures:--- http://technoanswers.blogspot.com/2011/06/how-to-replace-fuel-pump-on-lexus-ls.html ----------- For fuel filter replacing, click this link:--- http://technoanswers.blogspot.com/2011/06/how-to-replace-fuel-filter-1994-lexus.html ----------- For timing belt and water pump removal and installation, click this link below:-- http://technoanswers.blogspot.com/2011/06/how-to-change-timing-belt-and-water.html ------------ For coolant flushing and filling, click the link below:-- http://technoanswers.blogspot.com/2011/06/how-to-drain-and-fill-coolant-on-lexus.html -------------- This all procedures should help.Thanks.Helpmech.

chk the gas drum under the engine

try the multiplug connection on top of the tank

yes you do, here are basic instructions for any in tank fuel pump. also remember to replace the fuel filter as well or warranty on pump is voided.

http://www.aa1car.com/library/fuel_pump_replace.htm

if your talking about thew gas gauge it is in the tank.

Ok look for a desconected or not installed negative, wire in the work area you was working

Hi.....
On your 91 Lexus ls 400.
If you remove the Rear passanger seat.
You will have axces to the fuel pump.
Remove the metal cover . Disconnect the wire harnes,
Disconnect the lines.
removing the nuts you will able to remove the fuel pump.

Ok.. I hope this help on your question.
Thank you for use fixya...

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