Major Electrical Problem (possibly)

[JohnNeedsHelp]

I have a 2015 Chevrolet Silverado and have noticed that my fuel mileage is 1.1 mpg. I hit the gas and it feels as if it is not getting the correct amount of gas to the engine. When it shifts down it shifts down harder than it should. I recently put a new motor in it a year ago and it only has around 50k miles on it. The check engine light states it is the O2 sensor. I have changed the sensor, fuel filter, and a couple of odd end things and still not fixed the issue. 

 

I was told that it was the computer and purchased a new one and when it was installed the vehicle did not accept it and would not work (it was the correct part and number I double checked). I was told it was an issue with the internal part of the motor, I can't remember what it was, and one day while it was raining my headlights began to flash while the vehicle was completely off. I have been told by three shops that it was an electrical issue and could be a short or crimp in the wire.

 

I have had this problem for over a year and it has been to five different shops and no one can fix the problem. Any help or things that I can try to fix the issue?

[newdude]

What codes do you have?  As in the actual code number?

 

You mention changing a fuel filter.  The gas trucks don't have one other than the strainer on the fuel pump internal to the tank.

[asilverblazer]

4 hours ago, JohnNeedsHelp said:

I have a 2015 Chevrolet Silverado and have noticed that my fuel mileage is 1.1 mpg.

Fuel mileage is least of your problems.

 

4 hours ago, JohnNeedsHelp said:

I hit the gas and it feels as if it is not getting the correct amount of gas to the engine.

It most definitely is NOT.

 

4 hours ago, JohnNeedsHelp said:

When it shifts down it shifts down harder than it should.

Probably in limp mode.

 

4 hours ago, JohnNeedsHelp said:

I recently put a new motor in it a year ago and it only has around 50k miles on it.

Why? Was the engine of the correct year, make, model, type? A 2015 should not have needed a new engine. Mileage on the chassis?

 

4 hours ago, JohnNeedsHelp said:

The check engine light states it is the O2 sensor.

What is the actual code?

 

4 hours ago, JohnNeedsHelp said:

I was told that it was the computer and purchased a new one and when it was installed the vehicle did not accept it and would not work (it was the correct part and number I double checked).

New computer wasn't/isn't correctly programmed. The old computer should work if the new engine and associated hardware is correct. I would put it back in and see what codes (problems) it detects.

 

4 hours ago, JohnNeedsHelp said:

I was told it was an issue with the internal part of the motor, I can't remember what it was

Could be but I doubt it.

 

4 hours ago, JohnNeedsHelp said:

one day while it was raining my headlights began to flash while the vehicle was completely off. I have been told by three shops that it was an electrical issue and could be a short or crimp in the wire.

I doubt this is connected to your engine performance and is a separate issue to be diagnosed.

 

4 hours ago, JohnNeedsHelp said:

I have had this problem for over a year and it has been to five different shops and no one can fix the problem. Any help or things that I can try to fix the issue?

So you have a replacement engine in the truck with the old PCM and the only code is an O2 sensor code? 

 

There are 4 total O2 sensors, only 2 of them control engine performance. Was the correct one replaced? Next, inspect the condition of the wiring and plug connections.

 

List any other deviations from a stock truck.

[rlcole321]

Well "John needs help", thats for sure, only thing I can say is "Dealership", I know most don't like it, but in your case, you HAVE to get the right programming done to start!