[recon9]

This has happened to me too on long drives. I've always seemed to have noticed it when the sun is low in the sky. I figured that was throwing off the sensor.

 

[GeorgiaBoy]

I've had this happen twice a 19EX, both times about half way into a 10 hr. drive on a major wide open highway. Once in rainy weather, once in clear and both times it re-set its self after a restart.

The BCW (Blind-Spot Collision Warning, Kia's terminology for BSD, not mine) function is explained in section 5 in the US manual and one of the more notable comments is "• The system may turn off due to strong electromagnetic interference". Interference from what? Radio, micro wave, cell phones, perhaps another cars FCW/RCW/BCW system?

Go figure.

 

[bobdec]

Blind spot uses K band radar, the low power antennas on the car are tuned to aim specifically into the blind spot (side and rear) areas of the car, limiting their transmitting capability. However radar jammers, and other radar transmitters received by the antennas could be confusing the receiver. If you have ever used K band radar detectors you may remember experiencing false alerts at times. My guess is maybe other vehicles with radar electronics active, police radar transmitting, may have been picked up by the BSD antennas. Not being a communications transmission specialist I can't answer the microwave, but I don't think radio transmission or cell phone will overlap with K band frequencies. Communications experts are welcomed to chime in.

 

[ecanderson]

K band radar is clear up at 24GHz, WAY beyond any cell phone (figure max 1.8GHz). Ka band is even higher, up around ~35GHz.

Being in the presence of a strong legitimate K (or perhaps even Ka, depending upon the selectivity of the system) could 'swamp' the input of the car's system. As someone noted, there are jammers out there (illegal, but out there) that could certainly also have the same impact on the car's system.

At their much lower frequency, they wouldn't/shouldn't bother the car's system, but also to point out that GPS systems can be wonked by GPS jammers (~1.2GHz to ~1.6GHz, too. There's more of them out there than anyone realizes.
Newark Airport used to have a LOT of trouble with GPS jammers on the adjacent highway screwing up their operations.

 

[GeorgiaBoy]

I got it, sun spots! Yeah, that's the ticket!