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sprinkles08
sprinkles08, Chrysler/Dodge/Jeep master tech
Category: Dodge
Satisfied Customers: 21805
Experience:  ASE Master and Advanced Certified, Chrysler/Dodge/Jeep Master Certified, Trans and Hybrid Specialist
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98 dodge grandcaravan

Customer Question

98 dodge grandcaravan
Submitted: 10 months ago.
Category: Dodge
Expert:  Ron replied 10 months ago.

Hello and thank you for you post,

Can you please tell me what your needing with as many details as possible please?

Customer: replied 10 months ago.
the gas gauge drops to empty once it passes the half, mark, and if top it off it will read fine untill passes the half mark, the fuel pump assembly has been replace several times. any ideas.
Expert:  Ron replied 10 months ago.

The fuel gauge is controlled by the BCM (body control module ) . Are you able to scan the system and see if there are any fault codes setting?

Customer: replied 10 months ago.
Engine Code P0463 - Fuel level sensor high.
Expert:  Ron replied 10 months ago.

The common cause for this code to set is usually a failing sending unit and or the circuit to it. Since you have replaced the sending unit then I would suspect its a wiring concern or a faulty replacement sending unit. The BCM updates the PCM on fuel level status. If the PCM sees that voltage is high for too long, it sets a P0463 code. This sure sounds like you may have a defective sending unit.

Customer: replied 10 months ago.
i have replaced it twice in this past month, and they both have the same symptoms, when i check the voltage to the signal wire at the fuel pump, i get source voltage, ( fuel pump disconneted) and 5v when connected.
Expert:  Ron replied 10 months ago.

Okay well Im afraid this is something I am not going to be able to fix from there. Ill open the post back up for you in hopes someone has ran across this issue before. If they can help you they will post back.

Customer: replied 10 months ago.
thank you sir.
Customer: replied 10 months ago.
were you able to transfer me to another tech?
Expert:  sprinkles08 replied 10 months ago.

Hello and welcome to JustAnswer!

This code sets when the fuel sender's signal circuit goes high. If the sender has been ruled out then the problem has to be wiring, connections, or possibly a failure in the body controller.

Electrical testing would need to be done at the time the gauge is dropped out, otherwise results will not be valid. At the time the gauge is dropped out the sensor ground will need to be tested as well as testing the signal wire for a short to voltage. If pullup voltage on the signal wire is missing then the wire is open between the BCM and pump. The signal wire can also be grounded to see if the gauge momentarily climbs and a code sets for fuel sender volts low. If not then you either have a signal wire or BCM issue.

Customer: replied 10 months ago.
Key on, engine off, I jump the ground wire to the signal wire ,and I get 0v. When I cicle the on and with the jumper connected, the gauge moves momentarily, up and drops down to empty.
Expert:  sprinkles08 replied 10 months ago.

The signal wire and BCM are functioning correctly at that time then.

Customer: replied 10 months ago.
I guess I get back to you tomorrow, I'm not home, I have other testing that I wrote it down.
Expert:  sprinkles08 replied 10 months ago.

Ok.

Customer: replied 10 months ago.
okay sir, i have the truck running and check for voltage to + wire at the fuel pump connector and i get source voltage and i back probe the signal wire and i get 3.7v , the gas tank is right above the half tank. so basically if i refuel to the full tank it will work just fine, but as soon it get close the half of tank, need/gauge drop to empty and warning light come on. i replace the fuel pump twice.
Expert:  sprinkles08 replied 10 months ago.

The wiring needs to be tested at the time the gauge has dropped. If the ground and signal wire test good then the problem has to be the sender or the BCM, if you can ground the signal wire at that time and set a volts low code, and the pullup voltage is present with the connector unplugged then the wiring is ok. If the problem is dependent on fuel level there is little chance that the problem isn't the sender.

Customer: replied 10 months ago.
KEY ON ENGINE OFF I JUMPED THE GROUND TO THE SIGNAL WIRE AND THE SCANNER READ 0V. DOES THAT MEAN THE SYSTEM IS GOOD? AND THE FLOAT IS BAD?
Expert:  sprinkles08 replied 10 months ago.

That means the BCM and wiring are ok at this time.