Just want to share my experience replacing the BSM sensors on a 2009 CX-9 GT with 140K miles. The BSM started acting up 2~3 years ago. At the beginning, the light flashed in summer when ambient temperature was above 90F, but back to normal when it cooled and virtually no issue in the winter. Since then, then BSM gradually deteriorated over time. Second year, 75'ish and this year, it started flashing even the ambient was over 65F. When it didn't flash, the BSM didn't detect 90% of the time. After reading this thread and some other sites, I decided to replace both sensors myself. Bought a pair of version B used but visually in great shape on-line. The replacement turned out to be much easier than I anticipated. There is no need to remove the rear bumper. Here is what I did:
1. Remove the rear light assembly by loosening the two screws. This would exposed one clip underneath, remove it.
2. remove the two screws (7mm) of the wheel splash fender (I don't know its technical name). No need to remove the clip further far inside.
3. remove the clip of the black trim over the wheel. This would allow the trim to come loose.
4. Underneath the vehicle, remove the screw (7mm) that joints the splash fender with the bump cover. Then you can separate the two. Let the splash fender loosely hang there over the clip in step 2. After separation, it will expose another clip for the bumper cover. Remove it.
5. Pull the bumper cover toward you to disengage the hidden clips behind. You may need to yank a bit and apply some force. Don't be afraid, it will come loose.
At this point, you will have large enough gap to access the sensor bolts. The rest steps (removing bolts and disconnecting cable) are straightforward.
Tips for removing the bolt: they can be rusty. Use a wire brush to clean off the rusts, apply some oil or WD40. Keeping the rust /dust off and surface lubricated would help to prevent it from snapping, which was the mistake I made while loosening the first rusty bolt with too much torque.
It took me more than one hour to do the first side. After figuring out the tricks, it only took 30 minutes to do the other side.
No calibration is needed for the new sensors. The BSM now is working as new.
1. Remove the rear light assembly by loosening the two screws. This would exposed one clip underneath, remove it.
2. remove the two screws (7mm) of the wheel splash fender (I don't know its technical name). No need to remove the clip further far inside.
3. remove the clip of the black trim over the wheel. This would allow the trim to come loose.
4. Underneath the vehicle, remove the screw (7mm) that joints the splash fender with the bump cover. Then you can separate the two. Let the splash fender loosely hang there over the clip in step 2. After separation, it will expose another clip for the bumper cover. Remove it.
5. Pull the bumper cover toward you to disengage the hidden clips behind. You may need to yank a bit and apply some force. Don't be afraid, it will come loose.
At this point, you will have large enough gap to access the sensor bolts. The rest steps (removing bolts and disconnecting cable) are straightforward.
Tips for removing the bolt: they can be rusty. Use a wire brush to clean off the rusts, apply some oil or WD40. Keeping the rust /dust off and surface lubricated would help to prevent it from snapping, which was the mistake I made while loosening the first rusty bolt with too much torque.
It took me more than one hour to do the first side. After figuring out the tricks, it only took 30 minutes to do the other side.
No calibration is needed for the new sensors. The BSM now is working as new.
