No AM radio signal on two aftermarket HUs?

[tomkecil]

Originally Posted by barryware

it has been so long, I don't remember. I use the complete service manual download from a link on this forum to find the wire that is in the radio harness plug.. Not sure, but I remember it as being blue.

Using the harness I bought for my head unit.. I connected the wire to power the rf amp to the switched 12v wire to the head unit.

So.. when ever I turn on the ignition, the rf amp powers up.

I stumbled on this after Googling took me to lots of places. I had the same problem - AM dropping in and out and FM not nearly as good as it was with the original head unit. Both are now excellent on my 2007 Yaris sedan. If you're just finding this from a search here's the full picture:

removing old head unit
It took <1min to pop off the four fascia panels around the unit and undo the four screws that hold the deck in place. Easiest car I've installed on!

Mounting new head unit
I bought a single din Kenwood and a single din tray that's especially made for Toyotas and comes with the two black plastic 'filllers' that are the right size to fill the gap in the dash. The tray and fillers were $20 and fit perfectly - see picture

Connecting the cables
I bought a head unit wiring harness for later model Toyotas on eBay (~$12) and then soldered and heatshrinked the leads onto the other end of the harness that came with the Kenwood. As the harness was designed for ISO connections all the colours were a straight match to the Kenwood harness, so it was simple. I plugged it in and it all worked well except for the radio reception.

Fixing the radio reception
Thanks to the posts above and another search, I confirmed that the Yaris is fitted with a signal amplifier that sits in between the rear window antenna and the aerial lead in the dash. It received power from the old head unit via a lead in the factory harness that runs to the amp down the back of the car, but the new unit was not giving it power. The lead you're looking for is the all black one in the middle of the Yaris's blue plug. When you get 12V to it the reception returns to the great quality of the original head unit. The ISO Toyota harness pin that connects to that black lead is blue, and the Kenwood had a blue lead designed to switch those motorised antennas on when the head unit is on, so, connect blue to blue and the job's done.

I now have streaming bluetooth audio, good quality hands free phone calls (I mounted the supplied external microphone at the top of the trim on the driver's A pillar) and most importantly, a happy wife.