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Discussion Starter · #1 ·
2005 LLY, no tune installed. With the truck running, when I plug my code reader scanner into the OBDII port, many of the dash lights start flashing/blinking/”service 4wd”/fuel gauge goes to E, but the truck will drive fine. I unplug the scanner and everything returns to normal.

If the scanner is plugged into the truck first, then I try to start the truck, the truck starts and dies immediately.

This same scanner used to work fine in this truck, and it still works fine in my dad’s 2005 LLY and in various other vehicles.

I’ve checked various fuses, harnesses, etc.

Any ideas?
 

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Sounds like the high speed LAN is having problems. This is how all the modules in GM vehicles communicate.

Could be as simple as a bent pin on the connector or a failing module.

Check the resistance with a multimeter on the OBDII ports #6 and 14. Should be around 60 ohms with everything off.
 

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Discussion Starter · #3 ·
Hey there. I don't have a pins in 6 or 14. Those are can CAN protocol pin locations, right? Mine uses class 2 protocol. I have pins 2 (data), 4,5 (both grounds), and 16 (battery +). Would an ohms test still be useful? I'm getting 12v going from 16 to ground in door jamb, 16 to 4 and 16 to 5.
 

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Hey there. I don't have a pins in 6 or 14. Those are can CAN protocol pin locations, right? Mine uses class 2 protocol. I have pins 2 (data), 4,5 (both grounds), and 16 (battery +). Would an ohms test still be useful? I'm getting 12v going from 16 to ground in door jamb, 16 to 4 and 16 to 5.
My bad, yes those are the pins for CAN. Sorry I don't have any experience with the class 2 stuff other than the "old paperclip" code reader method in my third gen camaro.

I would check all the pins to ensure that they are in good condition (not gapped open or slipped out the back of the connector from plugging / unplugging the reader)
 
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