DTC B18B4: Left BSI Radar Unit Dirty

Check the outside of rear bumper for snow, ice, dirt, contaminants, or stickers.
From the left rear wheel arch, remove the screws securing the rear bumper (see step 2 under REAR BUMPER REMOVAL/INSTALLATION ).
Gently pull on the rear bumper (A) at the left rear wheel arch area to release it from the hooks (B) on the side spacer (C). Do not pull the rear bumper forcibly.

Fig 1: Pulling Rear Bumper At Left Rear
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Check the inside of the rear bumper for snow, ice, dirt, or contaminants. Also, check the left BSI radar unit surface for dirt or contaminants.
Is it OK?

YES -Intermittent failure due to temporary contamination around the rear bumper, the system is OK at this time.

NO -Go to step 5.
Remove the rear bumper (see REAR BUMPER REMOVAL/INSTALLATION ), and wipe off the dirt or contaminants.
Check the BSI radar unit bracket for proper installation (see step step 5 under ).
Is it OK?

YES -The troubleshooting is complete.

NO -Install the BSI radar unit bracket properly. If it is damaged, replace the left BSI radar unit (see BSI RADAR UNIT REMOVAL/INSTALLATION ).