The receiver module is essentially an ASWC-1 with an added RF receiver, and probably some custom firmware.
No surprise that their harness skipped connecting to SWC common (28-pin #23) -- the OEM HU gets the same ground from the HU's 10-pin power/speaker harness. You'd only need pin 23 when connecting a real OEM steering wheel with SWCs to the HU (or to an aftermarket interface module).
But I
am surprised it needs +12V Battery, when a normal ASWC doesn't. I wonder what they're doing with that? (in what situation would you want the RF SWCs to work while your key (+12V ACC) is off?). The module shouldn't be needing constant power to maintain memory (normal ASWCs don't).
Anyway, try confirming your HU is accepting SWC commands by disconnecting the receiver module and using resistors or a potentiometer to simulate the SWC resistors.
Quote:
SWC resistor values:
Code:
Pin 21:
Preset Up 0 Ohm
Preset Down 330 Ohm
Volume Up 1000 Ohm
Volume Down 3110 Ohm
No buttons 100K Ohm
Pin 22:
Mode 0 Ohm
On hook 330 Ohm
Off hook 1000 Ohm
Talk 3110 Ohm
No buttons 100K Ohm
(and you can just short the appropriate wires to simulate the 'preset up' and 'mode' functions).
Holding 'preset up' or 'preset down' more than briefly causes seek up/down. Holding 'mode' more than briefly causes mute/unmute.
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I've done that myself with an FT nav HU out of a 2013 BRZ, so it should work for you.
The module is looking for particular voltages on the wires that connect to the HU. It may also be looking at which pins were used on the 12-pin harness to determine the HU brand (potentially one of several different OEM types -- Toyota, GM, Chrysler, etc.).
I'm wondering if your choosing the OESWC-8113H is throwing off that logic. Download the installation manual for a normal ASWC-1 (
PDF link), and compare the harness pin-out in that manual to the 12-pin plug on your 8113H harness.
I haven't had my hands on an OESWC module (and the manual is a bit brief), so I don't know if it has the diagnostic blink codes and manual programming options like a normal ASWC-1.
You'll probably have to call Metra's tech support. I recommend that you verify all of the SWC resistances your OEM HU is looking for first. That will help avoid Metra claiming your BRZ's HU doesn't have SWC capability. They could still claim that the BRZ's differs somehow from other Toyota HUs (but I didn't think that was the case).