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2020 Kenworth T680 SPN 639 Communication Loss
I'm dealing with a concern on a 2020 Kenworth T680 where I'm seeing SPN 639. The check-engine light came on, and I received a transmission fault message. Interestingly, the vehicle is unable to shift from forward to reverse while stopped. These symptoms suggest a possible communication issue between the ECM and the SAE J1939 data link. What could connect these symptoms, and what should a qualified technician inspect first to address this issue? Any insights on what factors to consider would be appreciated.
Verified source: ODI 11629546 — SPN 639