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Discussion Starter · #1 ·
I have a number of malfunctions. I start trouble shooting by reading what DTC codes show up. What showed up was numerous DTC codes, most dealing with “ Lost Communications “. At that point I start looking for bad connections, shorts to ground, bad fuses and bad grounds. I learned years ago that I need not only check connections but also continuity of wires and connections. Batteries and cables checked good. Went to Underhood BEC (Fuse Center) next. All fuses good. Next step was to check continuity from where the positive battery cable connects through the fuses. This is where I need help! In checking the continuity I get zero resistance at some points and 200 ohms at others. Nothing in between. In my mind (which is not always as clear as it should be LOL) The fuses are plugging into a buss bar or plate and I should be getting zero resistance across all points of contact with or with out the fuses. I get the same readings with the fuses removed by testing one side of the female plug that the fuses plug into. It is hard to believe that the BEC is bad (although it may be) as I am getting the 200 ohms resistance reading at quite a few points, so many in fact that I don’t see how the truck would even be drivable. It would be greatly appreciated if some one could help me understand what I’m seeing. Why am I getting the 200 ohms resistance reading at points?

Thank You, Carl
 

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Helps to know what you are working on-!

Are you testing the ohm with the batteries connected-?
 

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Discussion Starter · #3 ·
Helps to know what you are working on-!

Are you testing the ohm with the batteries connected-?

NO! I have both POS. & NEG. cables disconnected. I like to test each component independently. I got a brand new cable a while back that was bad. Wire going into clamp was not making connection with clamp. Sucks when new parts are bad.
 

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You are better off doing a voltage test on the circuits that are giving you trouble. All fuses will have some resistance. They have to have more resistance than the overall circuit for them to work. If their resistance was low, they would not protect the circuit and the next weakest link would go down in flames. 200 ohms is excessive and if you are testing with both batteries disconnected, I think you may have found the source of your trouble. Good luck!
 

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Discussion Starter · #5 ·
lugnut;
Any fuse that I have ever checked that was good had zero or close to zero resistance. Please correct me if I'm wrong, a fuse has a filament in it that is capable of conducting a given amount of amps when exceeded burns away. With that said voltage is not relevant as far as the fuse.
You are right a voltage test will need to be done. How ever I get the same readings with the fuses removed by testing one side of the female plug that the fuses plug into.
I've got the following DTCs U1064, U1026, U1024, U1041, U1000 & U1301. I'm thinking rather than trying to chase down these individually, look at what is controlling the modules that set the DTCs
 

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Measuring resistance with a meter is only going to help you so much. A good quality 10 Mega Ohm impedance meter will only put out a very small amount of current at a very low voltage. This is why a typical fuse will measure low resistance. Once you do a voltage drop test across the fuse, you will see exactly what I am saying. The fuse will generate a voltage drop, which indicates resistance in the circuit. All fuses must do this to work properly. Here may be some interesting for you to watch. https://www.youtube.com/watch?annotation_id=annotation_703593&feature=iv&src_vid=d3_yWnUH2Sw&v=T6rDTtxaeJ4 This will explain the reason for resistance in a fuse.
 
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