Hello and welcome to Just answer,
What is the year and model , engine size of the vehicle?
Below is a diagram of the connector on the vehicle side with the colors and thier purpose. Let me know if you need help matching them up or need different information.
Connector Part Information
Fuel Level Sensor Signal [- Primary]
Fuel Pump Supply Voltage
The colors on the car are different. On the truck wiring harness the wires are blace, white, orange, green.
Just to clarify are these the colors of the wires that are on the fuel pump module or the connector on the truck leading to the module that plugs into the top of the module?
Has the trucks harness had a new connector installed for the fuel pump?
This is the only thing that makes since, GM has used Gray for fuel pump power and purple for sending unit signal for years.
On your fuel pump Grey is fuel pump power, Black pump ground, Purple is signal from fuel sender and purple with black is low reference fuel signal (ground)
Can you look at the connector below and match up the wire colors you have to the terminals labeled? for instance is term A orange?, ect.
On that square plug what position is each wire in on the plug and does it look like the connector I have sent already?
this is the only way I can help if I know this from you, I have the factory service info on your vehicle and I know it is correct from actual experience it is not matching up to what you are telling me. so I need to know the information above.