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Discussion Starter · #1 ·
I have EFI with a DSP5. I normally run it on tune 4. A few months ago I found a new Sunoco fuel stop. As soon as I started fueling there, the truck had a lot more power. It was like there was a position in between 4 and 5 but it was still in position 4. More power than tune 4 but less than tune 5. At first I thought it was the fuel. I thought "how could the tunes change?" Then a strange thing happened.

There is a hill on my commute home from work that I can only climb in overdrive if it is on tune 4. One day it had to downshift. It did it a couple times that day to get up the hill. It was a windy day so I figured that is what caused it. The next day, same thing. Downshifted to get up the hill. Then I realized it didn't have the extra power I recently gained. Actually, it had less than before the power gain.

I then selected tune 5. It now runs like it did when I started fueling at the Sunoco station. No downshifting and plenty of power again.

Here is the problem. Tune 5 is gone and is now tune 4. Tune 4 is now tune 3. I don't know about the rest.

Any ideas? Could it be a faulty DSP5 switch?
 

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Wow that was hard to follow.

Do you have a v-2 and efi live on a laptop? You need to see if your voltages are changing.
 

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Discussion Starter · #4 ·
Wow that was hard to follow.

Do you have a v-2 and efi live on a laptop? You need to see if your voltages are changing.
Ya, I knew that would be hard to follow. Did my best but feel free to ask for clarification.

I had my ECM programmed with the tunes by Danville Performance. I don't have any way of doing that.
 

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Then the only way to check the switch is to check resistance across the pins. If its changing then the switch is fine and you need to looks elsewhere for problems.
 

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Discussion Starter · #6 ·
Can a failed switch cause engine damage?
 

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No it will default to position 1 if it goes out of parameters.
 

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Discussion Starter · #8 ·
So I finally decided to get an Autocal package from Willie and Kory. Used the Autocal to test the switch, tested good. ECM was locked so couldn't load the tunes. Willie sent me to the dealer to flash it to stock. They couldn't do it either. My ECM is bad. That must be why my 5 tune is gone. A problem inside the ECM.


Sent from AutoGuide.com App
 
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