I have installed Apple Car Play via an adaptor unit and it works fine until I release the handbrake when it goes off. I presume this is so you can’t watch the front screen whilst driving. I have seen on the Mk2 there are 2 wires for the handbrake and speed sensor to disconnect, I presume it is the same for the 2006 Mk1 with the Toyota larger screen fitted. I have found wiring information for the Mk2 even information on the connectors at the rear of the head unit but nothing of use for the Mk1 Alphard. 

They look like more standard toyota connectors, should be the 5 pin grey connector, as this is commonly used on older headunits. (marked 12 on your photo)

 

Try this page:

https://pinoutguide.com/Car-Stereo-Toyota-Lexus/Toyota_Estima2003_head_unit_03_pinout.shtml

Edited August 21, 20223 yr by Chris.ac

If you have multimeter, you can confirm signal is going from a voltage, down to 0 volts when handbrake released, please let us know, so we can build on the knowledge

Yes you are correct, that is the connector, the wire colours No 1 blue with a yellow stripe No 3 red. I haven’t been out yet as the battery is on charge but it still works with the hand brake off

2 hours ago, Ayrshire Man said:

Yes you are correct, that is the connector, the wire colours No 1 blue with a yellow stripe No 3 red. I haven’t been out yet as the battery is on charge but it still works with the hand brake off

i think the pink stripped wire is reverse signal, too, if you need it.

2 is parking assist system

3 GPS antenna

 

6 Telemetric system (G-Book, Toyota assist)

7 not used on mine, not sure what this is

8 I think is external DVD/CD multichanger

 

13 is TV/DBT & antenna

 

Somewhere in the other connectors, you'd have Aux in (which you have already discovered) Electronic Toll Collection system, speakers etc, rear screen connection etc