Do you have something plugged into the cigar lighter that could be causing a problem?
"The cigar lighter provides 12 volt power (up to 15amps) to any device plugged into it. The Bulkhead Module (BHM) supplies power at this port regardless of the position of the ignition switch.
The BHM is capable of detecting short circuits in the cigar lighter wiring."
It could just be a intermittent connection at the Bulkhead Module (BHM). Remove all connectors from the BHM, check, clean, and reattach, confirming each connection it tight.
As mentioned these are complicated beasts with many systems that need to communicate the right information at the right time.
Here is the public Freightliner BHM service guide if you don't already have it; https://secure.freightliner.com/acce...a5412000wm.pdf
The code 33 is listed in the guide and there are also 15 references to the cigar lighter circuit which you would think is simple and irrelevant to engine operation but the guide says something a lot different.