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Doubeleive

Wes
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What would cause my EVAP code, and my fuel pump relay to not get any power
"No Communication” on every Control Module (ECM, TCM, BCM)
Tells me there is likely a short, most likely in the lan bus, inspect everywhere you can see and look for a pinched or chewed wire, melted wires, wire rubbing on a surface and chaffing (common). lift everything you can that sits on something else and look for frayed wires
take a meter and check the lan bus ohm's on the obd port, I believe they should be 5 ohm's but just going off memory. testing that will tell you if there is a short or open circuit.
 
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Blancotahoe

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"No Communication” on every Control Module (ECM, TCM, BCM)
Tells me there is likely a short, most likely in the lan bus, inspect everywhere you can see and look for a pinched or chewed wire, melted wires, wire rubbing on a surface and chaffing (common). lift everything you can that sits on something else and look for frayed wires
take a meter and check the lan bus ohm's on the obd port, I believe they should be 5 ohm's but just going off memory. testing that will tell you if there is a short or open circuit.
Where/ which prongs are the IAN bus
 

Doubeleive

Wes
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Getting 62 ohms car off and like 3 car on not sure how to properly diag with car on or off
Verify the high-speed LAN circuit integrity by measuring the resistance across DLC terminals 6 and 14 with a DVOM with the battery disconnected
if good then start pulling module fuses and re-testing communication after each fuse is removed
 
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Blancotahoe

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Verify the high-speed LAN circuit integrity by measuring the resistance across DLC terminals 6 and 14 with a DVOM with the battery disconnected
if good then start pulling module fuses and re-testing communication after each fuse is removed
61 ohms battery disconnected
 

Notch

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Had the same problem on my old 2007 Avalanache. The problem I had was the wiring loom shorted against the frame.

Sorry I don’t know exactly where since I had to tow it to a shop that found the problem.
But might be worth to take a look under truck at the wiring loom.
 

GMfan72

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All grounds have been fixed
Hi - you mentioned 'all grounds have been fixed' I had a similar issue with 'hood open' etc coming on. I eventually had to replace the ground wires. There is a ground wire on the Battery that goes to the engine block and continues to frame on the battery side. There is another ground wire on the drivers side that grounds the under hood fuse box , etc on that side of the vehicle. You may need to actually replace the ground wires.
 
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