Door ajar sensor for lift gate

New member, first post. I have a new to me 2016 SR5 Sequoia. The third row seats are power seats, and the rear controls do not work, and do not get power. The controls by the side doors work fine. According to the owners manual the rear controls can only be used when the ignition is in the lock position, the trans is in park, and the rear lift gate is open. I believe the problem is with the lift gate open sensor. When it is open, the dome light does not come on, and the door ajar light on dash does not activate. I cannot find the sensor that tells when the door is open. Can someone tell me where it is, and any guidance on trouble shooting it.