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Discussion Starter · #1 · (Edited)
hi
i need someone to help and measure voltage that receive by fuel sending unit from fuel gauge.i Mean the pink wire that goes to fuel sending unit not the fuel pump voltage.this is signal wire that comes from fuel Guage. on fuel pump connector that under backseat i think its third wire if you count from left. thanks
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I dont think anybody knows or has had a need to check.

The factory service manual doesnt state the information. At least I wasnt able to find it. All I could find was ohm information in testing the sender itself.

Wiring diagrams did not show the information either. 12v enters the instrument cluster, but possibly passes though a 5v regulator, and a 7v regulator, and enters a solid state control module, which also receives a 12v source too.

The testing procedure for checking the circuit specifies a 12v light bulb. So based on that, I would expect to see battery voltage on that wire.

But this is merely an educated guess.
 

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Discussion Starter · #4 ·
i have a short to ground in that circuit but unable to find it. can you tell me which wire gives instrument 12v?
I dont think anybody knows or has had a need to check.

The factory service manual doesnt state the information. At least I wasnt able to find it. All I could find was ohm information in testing the sender itself.

Wiring diagrams did not show the information either. 12v enters the instrument cluster, but possibly passes though a 5v regulator, and a 7v regulator, and enters a solid state control module, which also receives a 12v source too.

The testing procedure for checking the circuit specifies a 12v light bulb. So based on that, I would expect to see battery voltage on that wire.

But this is merely an educated guess.
i have a short to ground in that circuit but unable to find it. can you tell me which wire gives instrument 12v?
 

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Power is supplied by Fuse 17 10amp on the under dash fuse block

Its runs on the Pink/Black wire on pin 3 of the 20 pin connector to the instrument cluster.

It outputs on the Pink/Black wire on pin 18 of the same connector to pin 3 on the fuel pump (the one you pointed at)
 

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Discussion Starter · #6 ·
Power is supplied by Fuse 17 10amp on the under dash fuse block

Its runs on the Pink/Black wire on pin 3 of the 20 pin connector to the instrument cluster.

It outputs on the Pink/Black wire on pin 18 of the same connector to pin 3 on the fuel pump (the one you pointed at)
thanks a lot. how can i find my short in that circuit? it shorted to ground and have about 17k resistance between this pink signal wire and chassis. but manual says it should be infinite resistance.i have checked instrument cluster board and ecu connector and also bcm board but couldn't find any short. i have checked all the connectors in this circuit but nothing.i think its maybe on ignition switch circuit that supply 12v to instrument cluster but don't know where is this circuit
 

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You need to isolate each section of the circuit. If you had a short to ground on the power feed circuit (from fuse to cluster), then you would probably be blowing fuse 17.

If you have a short to ground on the output circuit (from cluster to fuel pump) then id imagine you could see an erratic gauge or a non functioning gauge.

Unplug the connectors from the instrument cluster and check for a ground signal on the pink/black wire (pin 3) at the fuel pump. You can simply check for voltage with your positive lead on the power pin (red wire pin 1) and put your negative lead on the pink/black wire. If it shows any kind of voltage response greater than .02v then you need to start tracing back the harness through the vehicle and look for any damages. More than likely Id be looking at the path down the side of the vehicle where the door sill is.
 

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Discussion Starter · #8 ·
You need to isolate each section of the circuit. If you had a short to ground on the power feed circuit (from fuse to cluster), then you would probably be blowing fuse 17.

If you have a short to ground on the output circuit (from cluster to fuel pump) then id imagine you could see an erratic gauge or a non functioning gauge.

Unplug the connectors from the instrument cluster and check for a ground signal on the pink/black wire (pin 3) at the fuel pump. You can simply check for voltage with your positive lead on the power pin (red wire pin 1) and put your negative lead on the pink/black wire. If it shows any kind of voltage response greater than .02v then you need to start tracing back the harness through the vehicle and look for any damages. More than likely Id be looking at the path down the side of the vehicle where the door sill is.
thanks for your information.no fuse has been blowed until now.thanks again
 

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Ok to check the fuse circuit, unplug the connector from the instrument cluster, and unplug the fuse. Put your leads to both terminals in the fuse location. If if shows voltage greater than .02v then your short is located on the wire from the fuse block to the cluster.

Btw, you must have the key in the ON position for both tests, otherwise there will be no power to test.
 

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Discussion Starter · #10 ·
Ok to check the fuse circuit, unplug the connector from the instrument cluster, and unplug the fuse. Put your leads to both terminals in the fuse location. If if shows voltage greater than .02v then your short is located on the wire from the fuse block to the cluster.

Btw, you must have the key in the ON position for both tests, otherwise there will be no power to test.
i will check tomorrow. yesterday when i checked fuel pump connector resistance between pink/black wire and chassis was 17k ohm.but when i checked same wire on connector under passenger side and near ecu there was about 90k ohm resistance. do you think its direct short or something shorted in a board like ecu or instrument because this high resistance normally isn't directly short
 

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If you dont have the instrument cluster connector unplugged, then all you are looking at is the resistance of all the components that circuit runs through. This is also why we check power and ground. Both will lead you to the correct answer, but the diagnostic must be performed correctly.
 

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Discussion Starter · #12 ·
If you dont have the instrument cluster connector unplugged, then all you are looking at is the resistance of all the components that circuit runs through. This is also why we check power and ground. Both will lead you to the correct answer, but the diagnostic must be performed correctly.
if i couldn't find my short can i use a dc to DC voltage regulator just before fuel pump connector to give signal wire correct voltage? that's why i ask for voltage measure on this wire at first post . if you give me the measurement when car running it's great help
 

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No, you cant do that. You could cause a fire in the vehicle. Im speaking from experience. Ive had other customers do similar things.

The reason your fuse blew is because wherever your short is, its pulling more than 10 amps. Its unrestricted power to ground. If you feed that circuit power, you are essentially bypassing the fuse, and feeding it as many amps as it can take.... which leads to an overload of the wire, causing it to get hot, causing it to melt, causing other wires to melt around it, causing bare wires to be exposed, allowing bare wires to touch each other, creating more shorts..... so on and so forth until something catches fire if it hasnt already by this point.

This is the same concept as just using a larger fuse until it stops blowing...... It will destroy the vehicle. You need to find the short and fix it, or pay somebody to do it. Or live with it broke, or sell it. Either way, there is no shortcut to this fix.
 

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Discussion Starter · #14 · (Edited)
No, you cant do that. You could cause a fire in the vehicle. Im speaking from experience. Ive had other customers do similar things.

The reason your fuse blew is because wherever your short is, its pulling more than 10 amps. Its unrestricted power to ground. If you feed that circuit power, you are essentially bypassing the fuse, and feeding it as many amps as it can take.... which leads to an overload of the wire, causing it to get hot, causing it to melt, causing other wires to melt around it, causing bare wires to be exposed, allowing bare wires to touch each other, creating more shorts..... so on and so forth until something catches fire if it hasnt already by this point.

This is the same concept as just using a larger fuse until it stops blowing...... It will destroy the vehicle. You need to find the short and fix it, or pay somebody to do it. Or live with it broke, or sell it. Either way, there is no shortcut to this fix.
i really enjoyed from your experience and knowledge and also your responsibility. as i mentioned before there was no blown fuse until know. i think this short made by me because of a mistake that i made three years ago and keep starting the car without fuel pump relay for about 10 times after that this problem shows up. i have checked schematic diagrams of instruments and fuel sending unit but what i didn't understand was wiring fuel sending unit to ecu.i see three pink/black wire on instrument cluster connector. two of them on 20 pin connector and 1 on another small connector. which one goes to ecu? or fuel sending unit wire goes directly to ecu from under driver side connectors? it confuse me to trace the short on separate circuits
edit**
also measured signal wire voltage on fuel pump connector. its has 7.30v when car running and 11.40v for about 20 seconds after car switched off. if you measure this for me i can find voltage difference
 

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Discussion Starter · #15 ·
and also measured signal wire voltage on fuel pump connector. its has 7.30v when car running and 11.40v for about 20 seconds after car switched off. if you measure this for me i can find voltage difference
 

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you have to check with the connector unplugged. You will get incorrect voltage readings while plugged in and the vehicle running.

The pink/black wire on pin 18 of the 20 pin connector from the instrument cluster goes to both the ECM and the fuel level sender, and the Black wire goes from the fuel level sender to the ECU, Instrument cluster, and Ground location.

You can ignore the black ground wire.

I did not see that the pink/black also goes to the ecu until now. You'll need to unplug both the ECU and The instrument cluster when testing that wire for a short to ground.


Edit: Also, I dont think starting the car without the relay would cause this because you havent bypassed any of the fuses, and the wires are separate circuits, nor do they share the same fuses.

You probably have something else going on.
 
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