Check that the body ground to tank is clean and tight. That's about the only thing that will cause this. Sending unit is good because the gage moves. Gage is good because it is working. Improperly, but it moves. It's getting power because it's moving. Only thing left is a faulty ground connection.
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
SOURCE: Gas gauge not working
Hi,
This sounds like the sender unit in the fuel tank is worn or possibly a corroded/ bad earth from the unit itself.
There should be an inspection plate above the fuel tank removal of this should reveal the sender unit and connections, if not can you see on top of it? make sure all connections are clean and not gunged up with corrosion. Try spraying Wd40 or similar around the area whilst wiggling the plugs/wires.
Good Luck, Please press the Blue Button to appraise my FREE! Effort.
Thank You!
Paul 'W' U.K.
SOURCE: I have a 1997 Chevy Blazer LS, the fuel gauge
all later model chevy vehicles are plagued with this problem it,s the fuel level sensor mounted on the fuel pump module inside fuel tank unfortunately on some models it,s only available with purchase of whole new fuel pump module that can run as much as $500.00 dollars for just the module not including labor to drop fuel tank and replace I encourage you not to waste time and money with aftermarket less expensive pump module assemblies not to knock any parts people but our shop just installed the 3rd napa fuel pump module in a 98 blazer because the new pump will not read correct amount of fuel finally it was replaced by a pump module assemblie from dealership at cost of $458.00 for pump it now reads correct hope this helps if you need more detailed instructions on how to replace repost at fix ya thanks
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