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Fuel gauge is stuck at empty

Tiny
SSROBERTSON
  • MEMBER
  • 2000 CHEVROLET SILVERADO
  • 4.8L
  • V8
  • 2WD
  • 175,000 MILES
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.
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Thursday, July 22nd, 2021 AT 2:06 AM

14 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
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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Thursday, July 22nd, 2021 AT 2:48 AM
Tiny
SSROBERTSON
  • MEMBER
  • 80 POSTS
Unplugged at the pump I don't get any voltage across the orange/black and purple wires with the key on.
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Thursday, July 22nd, 2021 AT 3:17 AM
Tiny
ASEMASTER6371
  • MECHANIC
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Check just the purple wire for power and ground the other lead to the body.

Roy
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Thursday, July 22nd, 2021 AT 3:23 AM
Tiny
SSROBERTSON
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  • 80 POSTS
.01 volt (set at 20v on multimeter) unplugged at fuel pump with key on.
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Thursday, July 22nd, 2021 AT 3:36 AM
Tiny
ASEMASTER6371
  • MECHANIC
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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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Thursday, July 22nd, 2021 AT 3:48 AM
Tiny
SSROBERTSON
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  • 80 POSTS
Same voltage as the rear. And verified ground on pin 80 as good.
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Thursday, July 22nd, 2021 AT 4:31 AM
Tiny
ASEMASTER6371
  • MECHANIC
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From the ECM? The purple wire?

Roy
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Thursday, July 22nd, 2021 AT 4:45 AM
Tiny
SSROBERTSON
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  • 80 POSTS
Yes.
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Thursday, July 22nd, 2021 AT 4:46 AM
Tiny
ASEMASTER6371
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If you have no voltage from the ECM, the ECM is the issue.

Roy
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Thursday, July 22nd, 2021 AT 4:58 AM
Tiny
SSROBERTSON
  • MEMBER
  • 80 POSTS
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?
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Thursday, July 22nd, 2021 AT 5:00 AM
Tiny
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
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Thursday, July 22nd, 2021 AT 5:05 AM
Tiny
SSROBERTSON
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  • 80 POSTS
Remanufactured ECM.
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Thursday, July 22nd, 2021 AT 5:07 AM
Tiny
SSROBERTSON
  • MEMBER
  • 80 POSTS
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.
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Thursday, July 22nd, 2021 AT 5:20 AM
Tiny
ASEMASTER6371
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You should have a warranty for your ECM.

No, the signal has to come from the ECM.

Roy
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Thursday, July 22nd, 2021 AT 5:32 AM

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