I am posting this here in hopes that someone will find this, and either report it to Pioneer or find this on Bing and know the solution. I dumped the firmware for both AVH-W4500NEX and AVH-W4400NEX and discovered there's an incompatibility between the new Bluetooth firmware in the iPhone 13 Pro Max and the unit's handshake code. Upon initial startup, the unit doesn't properly search for active Bluetooth 5.1 units, and it doesn't see it. But if you connect to it manually, it will initiate the handshake. I could fix this myself in IDA, however I don't have their key to resign the firmware and release it, and I don't care enough to brute force it, because I just bought a $30 thing I stuck in my air vent that holds the phone. All I need it to do is play music out of the speakers, so I just click connect on the device each time. I don't really drive all that much and it doesn't take long to click two buttons. Hope this helps. I posted this on Apple's forum but they purged it for being off-topic.
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