I don't have a Toyota Sienna van (though I used to own one a few years ago and agree that they're a great example of van-as-car rather than the old days of van-as-truck) but I do own a Toyota Highlander and I'm pretty sure that the Toyota navigational GPS system is standard across the line. If you have one, it's going to be the same as the one I have. Now, yours might be a bit more recent, mine is as-installed in a 2008 Highlander, but from what I've seen of other model years, it doesn't seem to have changed that much across the years...

As you might know if you've done this before, pairing a bluetooth device with a car nav system can be a bit of a hassle so I do want to set expectations before we go further. There are steps you have to take on the car system then steps you need to take on the phone, back and forth, until you're done.

Then again, there's no penalty for having to try this more than once, so let's jump in!

First off, on your dashboard you should see a row of buttons below the Toyo nav system screen like this:

Push on the "INFO" button to proceed. It'll show you the following primary options on the GPS screen:

As I've indicated, you want to tap on the "Telephone" button to set up your BT connection.

It's a bit confusing here because it's acting as if you already have a phone paired, but as you can see on the top right, there's a "NO CONNECT" warning message too. No worries, though, ignore all the dial display buttons and tap on "Settings" on the lower left.

Now we're getting nearer to the setup options. Good. Tap on "Bluetooth" here, but before you go further, notice also that there's a "Select Telephone" option. Very helpful if there's more than one driver / passenger who has a phone that you want paired with the Bluetooth in the car!

You can see that the device has the unimaginative name of "HANDSFREE" (instead of, say, "TOYOTA" or "YOUR CAR" or something). Tap on "Register" to add your phone to the car's Bluetooth database...

Great. Now we're -- finally! -- at the point where you need to switch to your iPhone and go through the steps on that side to pair the phone with the car Bluetooth system. Ready?

On your iPhone tap on the "Settings" icon, then look for "General":

Tap on "General" and you'll see a bunch of useful options that I definitely encourage you to explore. But not right now. For now, tap on "Bluetooth" and let's see how it's configured:

The most important thing is to ensure that your Bluetooth is turned ON on your iPhone. Makes sense, right? You might already have other BT devices known to your phone, like a headset or, in my case, my computer. The new HANDSFREE device should appear pretty quickly if you're sitting in your car, which is what I assume you're doing if you're trying to pair things!

To pair the "Handsfree" (odd how it's called "HANDSFREE" on the Toyota screen) tap on it here on the Bluetooth setup screen...

That's what we want. Now look on the Toyota nav system screen and you'll see that there's a Passkey code being displayed, 1 1 1 1. That's what you need to enter here on the iPhone (well, whatever your displayed code is, but I'm betting it's also 1 1 1 1). Enter it successfully before the car Bluetooth system times out and you'll see:

Done! Connected! Try it now, make a phone call on your iPhone and you'll see that the car system will automatically take it over and let you talk hands free. Smart, safe and easy.