DTC B18B5: Right BSI Radar Unit Dirty

Check the outside of rear bumper for snow, ice, dirt, contaminants, or stickers.
Remove the bolts on rear bumper wheel arch (see FRONT BUMPER SKID TRIM REPLACEMENT ). Gently pull on the rear bumper (A) at the wheel arch areas to release it from the hooks (B) on the side spacers (C). Do not pull the rear bumper forcibly.

Fig 1: Pulling Rear Bumper At Wheel Arch Areas
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Check the inside of rear bumper for snow, ice, dirt, or contaminants. Also, check the 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. Clear the DTCs.

NO -Go to step 4.
Remove the rear bumper, and wipe off any dirt or contaminants.
Check the sensor cover for proper installation.
Is it OK?

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

NO -Install the sensor cover properly. If it is damaged, replace it.