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06 duramax

C

clcreek

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I just bought a used 06 Duramax, 2500HD crewcab, about a week ago. Two days ago I found a red switch under the dash that was added by the previous owner (bought it from a dealer so I did not meet them) so I flipped it and the check engine light comes on, but I can't tell if anything else happened. So I crawl under the dash and find that the switch is tied into the wiring harness with a fuse.

I then put a code reader on the truck and there are no codes but I can't clear the check engine light. The next day the light goes out.

So today I do it all again. Flip the switch, check engine light comes on, with the switch flipped I try to read the codes but no codes and can't clear the light, flip the switch back try to read the codes but no codes and can't clear the light.

Anyone have a clue what this switch might be disabling/enabling in the system? I also can find no clues that there was any other aftermarket equipment installed in this truck.

Thank you!

This is also my first diesel...
 
Could be a "Smoke Switch". Go for a Drive, not too Far from Home (Just in case) and Flip the Switch and Lay into the Throttle and See if it Pours Smoke.
 
The switch would basically hold the vanes in the turbo charger open, causing low boost and making your truck smoke like a mother.
 
I'm thinking smoke switch as well, but hope that I am wrong.

Did the truck come with gauges? Any evidence of a pyrometer plug on the passenger side exhaust manifold?
 
Take truck back to dealer. Have them check the program in the computer to make sure it is stock. This could affect your warranty. If the dealer sold it with a warranty NOW is the time to clear this up before they say "You did it." as far as a warranty voiding power program.

The dealer can also find out what the switch is for.
 
FYI, '06 did not have the 5yr 100k powertrain deal so this one is out of warranty. Hopefully the dealer gave you a 30 day or so.
Anyhow, X3 on take it back to them about the switch.
 
This morning I went under the dash and pulled off all the tape, removed the switch, and taped all the wires that were involved and now the check engine light is out.

I thought about taking it back and accusing the dealer of trying to cheat the smog laws (check engine light on = no pass smog, and this was a way to cheat the light) to try and make him figure it out, but removing the switch and taping the wires seems to have removed the issue.

From what I have read it does look like a high idol switch that was cut off.

Thank you!
 
Maybe you can get the information on the previous owner of the truck and ask him what it was for your own piece of mind. Does the truck have the DIC switches on the steering wheel?
 
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