If it is of any use, here is my log. In my case, the n900 is getting a connection to the elm327 device.

libobd[INFO](obdcon_opendev:174): Connected to serial "/dev/rfcomm0"
libobd[INFO](obdchan_setup_channel:95): Trying ELM ...
libobd[RAW_DATA]: Sending to ELM -> 'AT|'
libobd[RAW_DATA]: Recieved from ELM -> '?||>'
libobd[RAW_DATA]: Sending to ELM -> 'ATZ|'
libobd[RAW_DATA]: Recieved from ELM -> '||ELM327 v1.4||>'
libobd[RAW_DATA]: Sending to ELM -> 'ATE0|'
libobd[RAW_DATA]: Recieved from ELM -> 'ATE0|OK||>'
libobd[INFO](obdchanelm_setup:463): ELM echo disabled
libobd[RAW_DATA]: Sending to ELM -> 'ATL0|'
libobd[RAW_DATA]: Recieved from ELM -> 'OK||>'
libobd[INFO](obdchanelm_setup:473): ELM linefeed off
libobd[RAW_DATA]: Sending to ELM -> 'ATST 19|'
libobd[RAW_DATA]: Recieved from ELM -> 'OK||>'
libobd[RAW_DATA]: Sending to ELM -> 'ATAT2|'
libobd[RAW_DATA]: Recieved from ELM -> 'OK||>'
libobd[RAW_DATA]: Sending to ELM -> '0101|'
DEBUG [14:20:28.295275] trip.c:0155 - Saving trip data: (obd: 0 0) (gps: lat:0.000000 lon:0.000000
libobd[RAW_DATA]: Recieved from ELM -> '41 01 00 00 00 00 ||>'
libobd[INFO](obdchan_setup_channel:97): ELM setup operation succeed!
INFO [14:20:30.580706] obd-thread.c:0469 - OBD device is ready
DEBUG [14:20:30.581042] obd-thread.c:0352 - STATE CHANGED: from 6 to 7
DEBUG [14:20:30.581225] obd-thread.c:0233 - unblock() called, reason: C
DEBUG [14:20:30.581438] obd-sched.c:0091 - Time scheduled pid: 13 is on the rlist. Ignoring
DEBUG [14:20:30.581591] obd-sched.c:0099 - Time scheduled pid 1 is not on the rlist, proceeding...

HTH.