IPA Back in mode no longer works on right side

I have a Gen III Prius with the Advanced Technology Package. Until recently, everything worked fine with the IPA system, in both parallel and back-in modes, to the left and to the right.

A few months ago, I hit a small deer. Other than a fog light and crack in the front bumper, everything worked fine afterwards, including the IPA. After having the bumper replaced by my dealership's body shop, I noticed that using the pre-assist function with the back in mode while parking in a spot on the right no longer functioned properly. While driving through the lot, scanning for a spot, pre-assist would initiate my turn well before the desired spot and, after shifting into reverse, would highlight a spot already occupied. If it didn't do this, it would initiate the turn in the correct location but then tell me that the space was not large enough, which of course was not the case because it could detect the same spot when it was on the left.

I have done this dozens of times with the exact same results. I brought my car to the dealership, and they swapped the sensors in the front bumper to try and eliminate this item (B.T.W., what kind of sensors are these? Sonar?). After swapping the sensors, they told me everything was working properly. My initial suspicion was that either something was loose or not seated properly, so when they told me this fixed the problem I didn't challenge them. However, today I had a chance to test the system again and it's still not working.

My questions are as follows:
1. Is there any other component in the front bumper that could have gotten messed up when it was replaced?
2. If not, it appears the front sensor works (parallel parking pre-assist works fine). How does IPA detect when the back of the car is in the right place? Camera?
3. If it is not the sensor in the bumper, it appears the issue had nothing to do with the bumper getting replaced. I suspect the dealership is going to point their finger at the body shop (owned by the same dealership), and the body shop will probably claim it didn't work beforehand and try to run it through my insurance company.

I would like to troubleshoot this issue myself as far as possible so I know how to move forward. Is there any information I can get regarding this system from an OBD-II???

Thanks.

 

It was a crap shoot between going to the dealership and the body shop. I gave the dealership a shot first because they would probably be more capable of troubleshooting the issue and also because I can get them to look at it while waiting, while the body shop would certainly require a drop off. Now that I know what it's not, I will probably take it to the body shop.

I have some questions regarding the link you sent me to. The post references four sensors in the rear bumper. This is the first I have heard about any sensors in the rear bumper. Are there any sensors there?

 

Doing some additional testing last night, I have been able to narrow down the circumstances in which this problem occurs. Using back-in mode, when I activate pre-assist, IPA almost always immediately detects an available spot next to me, even when one isn't there. If I follow the turn commands, I am quickly told the spot is not big enough. I assume this error message is generated by the camera once I start making the turn. If this is the case, it appears the camera is working properly, and the problem is with the sensor on the right side of the front bumper. If I activate pre-assist while next to the open parking spot, everything appears to work correctly.

Since the dealership swapped left and right sensors, I can assume the sensors work properly and they are connected. This leads me to believe there is something in the bumper itself interfering with the sonar operation. Perhaps when they painted the bumper they failed to remove some sort of masking tape in the region of the sensor. I'll try to remove the sensor this evening and see if I can find anything. I know that the body shop is responsible for this but it will consume much less of my time to have a look at it myself than to part with the car for a full day so they can check it out.