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It looks like this was in the light duty category and they just moved it over this one, medium/heavy duty trucks a few minutes ago.
U0100 - Lost Communication With Engine Control Module
- Faulty Engine Control Module (ECM)
- ECM harness is open or shorted
- ECM circuit poor electrical connection
This code will cause the transmission to act up because there is no communication going on.
Start checking the harness and the pins for any oil, corrosion, etc at the ecm to make sure there are no issues there. Check the pins for good power going to the ECM. Check the Orange, red, and blue wires. Those are the power in wires. See that they all have a good 12 volts on all of them.
If so, then send the ECM/PCM out for testing.
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