Fuel gauge is stuck at empty

2000 CHEVROLET SILVERADO
175,000 MILES • 4.8L • V8 • 2WD
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SSROBERTSON
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  • 80 POSTS
I have changed instrument cluster, fuel pump and sending unit, and new ECM. Also tested a new body control module and cannot get the fuel gauge to respond. I have even hooked up the old pump assembly and moved the float manually still didn't read. I'm at a complete loss.
Jul 22, 2021 at 2:06 AM
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ASEMASTER6371
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Good morning,

I attached a wiring diagram for you below for the sender unit. You need to test for voltage at the connector and the ground. You should have 5 volts at the purple wire.

https://www.2carpros.com/articles/how-to-check-wiring

Use your voltmeter and put both leads into the connector and tell me the voltage.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Roy
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Jul 22, 2021 at 2:48 AM
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SSROBERTSON
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Unplugged at the pump I don't get any voltage across the orange/black and purple wires with the key on.
Jul 22, 2021 at 3:17 AM
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ASEMASTER6371
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Check just the purple wire for power and ground the other lead to the body.

Roy
Jul 22, 2021 at 3:23 AM
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SSROBERTSON
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.01 volt (set at 20v on multimeter) unplugged at fuel pump with key on.
Jul 22, 2021 at 3:36 AM
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ASEMASTER6371
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I attached the wiring diagram for you at the ECM. The blue connector contains the power output to the sender. It should be 5 volts.

The other is the red connector pin 80 is the ground.

Roy
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Jul 22, 2021 at 3:48 AM
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SSROBERTSON
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Same voltage as the rear. And verified ground on pin 80 as good.
Jul 22, 2021 at 4:31 AM
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ASEMASTER6371
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From the ECM? The purple wire?

Roy
Jul 22, 2021 at 4:45 AM
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SSROBERTSON
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Yes.
Jul 22, 2021 at 4:46 AM
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ASEMASTER6371
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If you have no voltage from the ECM, the ECM is the issue.

Roy
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Jul 22, 2021 at 4:58 AM
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SSROBERTSON
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I just replaced the ECM yesterday. This was the exact same problem the old one had. Could it be the signal going to the ECM?
Jul 22, 2021 at 5:00 AM
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ASEMASTER6371
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Was the ECM new or used?

No, the signal is generated by the ECM out to the sender and then comes back on the return side. The fact you have no 5-volt reference tells me you have a bad ECM.

Roy
Jul 22, 2021 at 5:05 AM
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SSROBERTSON
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Remanufactured ECM.
Jul 22, 2021 at 5:07 AM
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SSROBERTSON
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Can I just use a 12 volt to 5 volt driver to resolve this issue? It's the only problem I'm having with the ECM and it's starting to get expensive just throwing parts at it.
Jul 22, 2021 at 5:20 AM
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ASEMASTER6371
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You should have a warranty for your ECM.

No, the signal has to come from the ECM.

Roy
Jul 22, 2021 at 5:32 AM