P0643 Primary 5 volt circuit high. What does this mean?

[Chris Mallett]

Not yet, I have been trying to take care of a customers truck...I will get back to mine tomorrow. Thanks for all of your help so far...I am hoping I can find this easily...

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2005 QC LB Dually, 4x4, F1 Helix 2 Cam, Sportsman springs, Fluidampnr, Edge Juice w/Attitude, Smarty, S&B Cold air intake, Needing tranny goodies badly.

Check out the West Virginia Cummins Crew

[JWH_03_Dodge]

Sounds good, probably won't be on here much til late tomorrow afternoon good luck

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'03 2500, 4x4, 5sp, QCLB, 90hp injectors, Glacier Fuel System, Quad Race Box, 5" exhaust, still looking for my silencer ring and muffler

[Kwilkinson]

It could possibly be more than just the fan 5 volt reference... These trucks base everything on a 5 volt reference that the ECM sends to the sensor, and when a signal comes back it is read by the amount of voltage drop, respectively. You could have some other sensor that has a shorted 5v reference and could be causing a malfunction to show up elsewhere. I would start at the fan, however, since that is a code you are getting. Check your 5v reference at the plug, check for ground, etc. I have seen the wires for the fan short before... so take a good look at everything. Shorted 5v references can mess with anything and everything not related to the actual problem

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07 Silver QC/SB 2500 5.9L Auto
A few go fast goodies
473hp 992tq 14.2 1/4 mile

[JWH_03_Dodge]

read back a couple posts, first step is unplug the fan because its the easiest and it gives you somewhere easy to probe it. 2nd step is unplugging the fan and ecm and checking for voltage and ground on that wire.

As long as he follows as much of the troubleshooting procedure as he can, he should be able to figure it out. Chris seems pretty sharp.

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'03 2500, 4x4, 5sp, QCLB, 90hp injectors, Glacier Fuel System, Quad Race Box, 5" exhaust, still looking for my silencer ring and muffler

[Chris Mallett]

JWH, you are a very wise person...I unplugged the fan, started the truck,(which I did not have to unplug it) and the only code was the p0483 fan speed code. THANK YOU FOR THIS INFO...I will be ordering a clutch tomorrow. Chris

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2005 QC LB Dually, 4x4, F1 Helix 2 Cam, Sportsman springs, Fluidampnr, Edge Juice w/Attitude, Smarty, S&B Cold air intake, Needing tranny goodies badly.

Check out the West Virginia Cummins Crew

[Chris Mallett]

BTW, This is why I am here, if I need help, someone always seems to know...If someone else needs help, and I know, I try to help the best I can. I will never leave this site, UNLESS BBRam kicks me out.

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2005 QC LB Dually, 4x4, F1 Helix 2 Cam, Sportsman springs, Fluidampnr, Edge Juice w/Attitude, Smarty, S&B Cold air intake, Needing tranny goodies badly.

Check out the West Virginia Cummins Crew

[JWH_03_Dodge]

I only try to help on stuff I know or have experience with. Glad I could help

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'03 2500, 4x4, 5sp, QCLB, 90hp injectors, Glacier Fuel System, Quad Race Box, 5" exhaust, still looking for my silencer ring and muffler