Factory Stereo harness adaptors (RHOK)

Sat, 11 Apr 2015 16:37:01 GMT

Taken from http://stephenmason.com/cars/mr2pc9406.html?hc_location=ufi

and saved here for posterity in case the original disappears

Autoleads PC9-406 stereo adapter

This page contains an overview of the Autoleads PC9-406 stereo adapter. This adapter allows for the plug-n-play installation of an aftermarket head unit in 91 Toyota MR2s with the premium sound option. The premium sound system uses a 14 pin harness that does not fit any of the Metra adapters. Using the PC9-406 harness allows you to install an aftermarket head unit while retaining the stock amplifier and without having to cut any wires. If you're not planning on keeping the stock amps, you can still use the PC9-406 to get your power and ground leads and such, but it's probably overkill.
For reference, here's pics of both the 14 pin and 15 pin stock body side audio harness. The PC9-406 only works with the 14 pin connector.

The pictures were taken from this thread and this thread.
This page just covers the adapter. Information about the MR2 premium system in general, as well as other approaches that don't rely on using the PC9-406, can be found here. I strongly suggest reading this discussion thread as well for some important background info.

Disclaimers:

The information here was current when I wrote it. Part numbers and part availability can change. If you notice something seriously wrong on this page, let me know and I'll try to keep it updated.
Use this guide at your own risk. Not responsible for blown speakers, electrical fires, or profanity overheard by impressionable family members.
This guide is a work in progress. Comments and corrections are welcome and should be sent to "smspam @ comcast.net" with "pc9-406" in the subject line.

Overview

The PC9-406 wiring harness adapter is made by a UK company called Autoleads. As of October '05, the only distributor I found willing to ship to the states was SIO communications, Inc. The price was 29.99 GBP. With the exchange rate and international shipping, it worked out to ~$57 delivered.
The packaging and harness are shown below.

The kit also includes an adapter to provide two female RCA connectors for head units that only have speaker line outs. As just about every aftermarket head unit these days has RCA pre-outs, it's unlikely you'll need this. Here's what's in the box:

PC9-406 wiring diagram

The following table lists the connections provided by the PC9-406. In short, it's in agreement with the mapping described in this thread .

PC9-406 Adapter Pin-outPin #BGB labelPC9-406 Connection1AMPblue-white wire with male bullet connector2ILL+orange wire in ISO B3+Byellow wire in ISO A4MUTEblue-black wire with female bullet connector5FL+Front left RCA plug center6FR+Front Right RCA plug center7ANTblue wire in ISO D8ILL-no lead present9ACCred wire in ISO E10GNDblack wire in ISO C11GNDConnected to ALL FOUR RCA signal grounds12BEEPbrown wire with "beep" label, butt splice crimp connector13RL+Rear Left RCA plug center14RR+Rear Right RCA plug centerNote that as shown in the photo below, the pins are numbered right to left so as to be consistent with the BGB convention for male connectors.

The ground, constant power, switched power, illumination, and antenna wire all terminate in an ISO female 8 pin connector. The labeling convention I used for ISO connector is shown below.

Note that the connections conform to the ISO standard for the power plug ("A-PLUG"), so you might be able to plug this directly into your aftermarket head unit. Be sure to check the manual for your head unit first, though, and confirm that the leads are going to the correct places. Diagrams of the ISO power (A-plug) and speaker (B-plug) connections can be found here and here

Lastly, for completeness, here's some pics of the wire side of the connectors and the RCA & bullet leads.

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