Electromagnetic parking sensor notes...

Most folks are trying to disable the beeping, but I craved it ...in a sense. After I took delivery of my PiP, I quickly disabled the annoying constant reverse beeping, but in my daily parallel parking, I realized that I was really missing the parking sensors that I've had on other cars for the last 10 years. Frustrating that this isn't a standard offering on the Prius.

After looking into it, I realized that they could be had as either Toyota or aftermarket accessories, and I also found that there was an electromagnetic option in addition to the typical ultrasonic sensors. I decided to take the plunge with a $15 electromagnetic kit from eBay, thinking it was worth a shot, given that I didn't even need to drill the bumper for installation. A simple search will give you dozens of options, but their operation is basically identical.

The kit consists of a sensor strip (basically a roll of metal tape), a small controller, and a speaker. (you can get some with LED indicators, but that seemed a bit hokey to me) The tape strip gets placed on the inside surface of the rear bumper skin, and a single wire leads to the control unit. A couple notes about sensor placement: close proximity to metal objects, such as body panels, will confuse the system. I found this out the hard way, as I originally placed the strip near the body line/crease near the top of the gen III rear bumper. Dry run testing worked fine, but it would never work when I put everything back together. As it turns out, the hatch was causing interference, and I always done testing with the hatch open. Took me about a day to figure that out... Eventually, I moved the strip down about 4-5 inches, and everything has been peachy. Note that the strip in my kit was also a bit too long for the Prius bumper, but should NOT be cut! I simply turned both ends of the strip down at the edges of the bumper to include the rear bottom corners in the field.

Wiring was also dead simple. I brought the sensor lead in through a rubber plug in passenger side rear corner of the body (next to the battery). For ground, I used the taillight ground, and for +12v, I used the lead for the reverse light. The control unit and speaker are backed with double-stick tape, so I adhered them both inside the taillight panel. The speaker is not super-loud, being behind the panel at the rear of the vehicle, but it can be clearly heard, which was my goal.

I've been using this for about 5-6 weeks now, and it has met all my expectations, and I'm extremely pleased with the result for $15. One slight annoyance is that the sensor field sometimes picks up variations in the driving surface while reversing, such as driveway ramps, speedbumps, etc. I may try to optimize the sensor strip placement to help with this, but it's not a huge deal. Also, note that the electromagnetic sensors do NOT operate like a more typical ultrasonic sensor, in that they only register changes in the electromagnetic field. This is good and bad in that it is so sensitive that you can literally park 2cm away from an object, but also requires movement to register an object. In other words, if you're not moving, the system will not beep.

I hope this helps someone make the decision on whether the electromagnetic proximity sensors are right for them. In my opinion, the low cost and invisible installation make this the clear choice over ultrasonic, if you're willing to accept the tradeoffs.