My 2005 ram3500 Cummins just rolled over 400,000km, and the service 4wd light came on and the 4wd shift **** on the dash started flashing all modes (4hi 2hi and 4lo) all at the same time and then quit, hasn’t come back on yet. It’s stuck in 2hi which isn’t a bad thing but have been trying to troubleshoot the problem. Ran a diagnostic check and no codes, went into ABS and had a code for left front sensor circuit failure, didn’t give me a number for the code tho (cheap craftsman code reader). Checked harness from left front sensor and right front sensor for corrosion, continuity, etc all good, checked harness connections on transfer case shift motor, they were fine, checked fuse #43 under hood and it was good, disconnected batteries and reconnected, going to start pulling dash apart and inspecting the switch and the TCCM.....what am I doing wrong?

any help would be greatly appreciated!