Rear windshield wiper arm

Hello, I’m Pete from the Car Genius team at RepairPal. I’m sorry you’re dealing with this concern on your Toyota Sienna. In some cases the wiper arm can be installed when the wiper motor itself was not in the full rest position which can cause this concern. The first thing I recommend is removing the wiper arm completely then cycle on the ignition and turn off the rear wiper and give it about 10 seconds to fully park in its rested position. Then install the wiper arm to see if it operates properly again. If it still operates incorrectly then check and make sure you have the correct wiper arm for this vehicle and if it is then you may have an internal fault with the rear wiper motor assembly or linkage that will need to be checked into further to help identify which component is at fault needing to be repaired or replaced. If you’d like to find a trusted, certified repair shop in your area, you can check here: https://repairpal.com/certified. If you need more advice, or have any further questions about your vehicle, we’re here to help. Just give us a call at 877-913-1554 where we will be happy to assist!