Hi Richard,
Buy one of these: Alpine INE-W920 INEW920 iNEW920 AUX IN & OUT Pre Out Lead PreOut sub Rear Out
Works perfectly with the AVN2, once you’ve updated the Firmware 
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Hi Nick,
Now ordered.
Firmware already happy.
Many thanks.
Richard
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I played with the wiring after deciding on a possible couple of places for the sub. The most likely spot is here in the trim panel not-a-cubby-hole, or close by. I’ll add some protection on the back side against wet roof problems.
There is a recess within the frame in the back of the seat and it just about fits in it despite sticking out from the trim panel. It’s simply sitting there at the moment and I’ll make up some more secure brackets for it tomorrow.
The wiring is simple enough.
I’ll be using the top green fuse position (Audio 20A) for a piggyback fuse holder of the same type as that at the top for the dash-cam. But I’m not trimming the yellow power lead yet. I’ll only know the correct length to reach the fuse AFTER securing most of it neatly. And I’ve used a very handy Ground point (G15) just under the driver’ left elbow, and just visible in the first pic of this post.
I still don’t know what the dongle is for, but the Blue/Red wire comes out the Remote Control pin on the Alpine for switching on an external amp. The other wires go with the reversing cam wires to the little accessory socket (Camera Remote) that lives above the main Power & Speakers socket.
I unwrapped the looming tape and soldered in to the Blue/Red a proper Blue/White wire with output bullet. And we can see the dongle wires and Rev-cam wires go to Camera Remote socket.
Here I’ve re-wrapped the loom, added the adapter leads for Sub Pre-outs and crucially the Aux Video input. The three uncapped RCAs will have L, R. Video routed along the centre console when the triple RCA lead arrives. I’ll add that lead to the loom carrying Remote, Ipad, USB. The video wire going on to the boot is simply so I don’t need to take it all apart again when I upgrade the reversing camera.
Thursday I hope to finish tidying the leads under the dash and inside the console and put it all back together.
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I finally managed to refit the head-unit, but only after chopping off all the unused signal wires from the new Pre-Out-Aux connector.
The offcuts are resting on the mounting panel I was making while waiting for the 2metre long Y, L, R triple RCA lead. The panel needs a few more holes for convenience, but all those for location are in correct positions.
This panel fits nicely behind the trim, and a smaller off-cut from this bit of duralumin sheet will be a packing piece slightly thinner than the sandwiched lip of the trim recess.
The pair of M6 bolts are temporary handles to help me quickly offer up the panel to the back of the trim through the aperture instead of past a half lifted PRHT.
However I’ll also loop a pair of straps around the USW300 as belt and braces safety, because I don’t trust the ali chassis-threads holding the sub behind me in the event of a crash if only two M6 bolts secure it.
Some wiring pictures. On the first one I took great care to make sure the yellow power wire could not be damaged by the left hand self-tapper, which is a bit close!
And the final loom waiting for the sub. The video lead with the F-F adapter will connect to one coming from the rf-link receiver, and I’ll use the existing tap on the reverse light to power both transmitter and receiver, simply because the umbilical to the boot lid is too thin to also have a video lead.
And all put together again except the piggyback fuse is not yet in place and the mounting panel needs finishing. I ran out of time today with it being my turn to do domestic as well.
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A minor problem has arisen!
Five minutes into our drive out today it was all going superbly, until just before the last chance to turn around for home the TPMS light came on and also the brake light flashed briefly (maybe the handbrake switch, as it has not lit again except when I operate handbrake).
A minute later this was followed by the red SRS light.
And as I drove into the garage, this was followed by followed by the ABS light and the EML light.
All the fuses in both boxes check out OK, correct volts and no drop across them.
My OBD2 suggests U0121 “Lost communication with ABS controller.”
All the usual other engine parameters it can see are spot-on normal.
I have a sinking feeling I’ve disturbed some wiring when I put the head unit back, despite being careful not to force anything!
Any suggestions?
“mutter dark incantations” isn’t the sort of suggestion you’re really looking for, I guess? 
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Much muttering took place!
Then more time digging out data and measuring with test meter, everything OK!
So no joy. Grrr.
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I wish you well in tracking the issue down, Richard. You actually know far more than most of us here about anything related to electrics or audio, so we’re all rooting for you and eager to see what the issue turns out to be!
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!!! Believe it or not I’ve fixed it !!! 
Finger trouble (as we used to say at work) was the culprit, my fingers…
With all the finagling to re-insert the head-unit, I had forgotten to plug in the clever climate control block lurking below it; and crucially, that block has a CANBUS connection.
All electronic engineers know that an unterminated bus line can bounce all sorts of confusing reflections off that open-circuit end, and when these ghosts arrive at other elements sharing the bus confusion will arise. And it sure did.
The only remaining two dash lights after reconnecting the battery were the ABS and the skid wiggle. L<->R on the steering, switch off, and on again, and all is good.
All I need to do now is rescue from the bin two stiff plastic cards (cut-down and folded A4 file ends) I used to hold up the lumpy bits clear, and reinsert the head unit. That will be tomorrow morning when I feel fresh again.
As a proper electronics engineer I really should have twigged it sooner; everything was working , but the modules were not talking to each other! What’s left? The CANBUS system.
My only excuse is I retired in 2005, because I was getting stupid, and time has only made matters worse!
On the bright side the day was not entirely lost, because we had a lovely day wandering around the Ascott House (NT) and its gardens. It is definitely worth a visit, and while that was our first, it will not be our last.
The sun was a bit hot and despite proper cool floppy Tilley hat, long sleeves, sun block etc, I’m still feeling the unaccustomed warmth.
It was an ideal top down day, perfect for an MX5, but instead we used the Mazda3, so no photo opportunity for the 25AE.
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Simple fix in the end then Richard.
I’m having a go at fitting a reverse camera tomorrow, head unit out, rear hatch apart plus all parts of trim apart.
Would you believe it’s 2 screws holding it in and 2 screws holding the brain box for it in.
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Ah… the dreaded “lost communication” 
Glad you’ve got it sorted!
Finished installing the fat yellow power wire to the cabin fusebox.
It is amazing how quickly a fat bag of cable ties runs down. And the fuseholder.
I needed to shape the pins on the piggyback fuse adapter, they come square ended, but these cannot find their way into the Mazda fuse block. So some careful tapering on the corners (a bit like a fuse) and suddenly it becomes easy to plug it into the socket. Some masking tape on the back and sides of the file prevents me from damaging the rest of the plug or the other pin.
Some photos of the Climate Control plug, showing nineteen out of the twenty possible pins loaded. I have no idea what the colours mean,and they don’t match any of my out-dated info.
Pins 1-10
Pins 20-11 and only pin 18 is empty.
Metal-work now under way and might even be finished this evening.
Sub is working in the car now in a test fitting, not quite as it will finally be, but fixed to the mounting plate etc.
I had a play with adjusting equalisers and cross-overs etc, and it is almost good enough. More opportunities for experimentation now, I might just get there in the end.
Certainly reducing the low frequencies going to the door speakers removes much of the unpleasant boom at three distinct frequencies, mainly the 50Hz (door-skin drum), less of a problem the 80Hz (cone resonance), and finally the 100Hz first harmonic on the door.
The 100Hz door harmonic was slightly reduced after adding the Silent-coat. A bit more might help…
I’m reluctant to brace the skin against the internal crash structure because this will remove resilience against casual contacts by soft but heavy items.
Unfortunately, 100Hz is also a peak on the sub, but the Alpine equaliser can reduce this by compromising elsewhere.
Sub is not finally fitted right now because I still need to finish wiring in the new reversing camera to the Alpine, via the video input connection I added to the wiring for the Sub.
I tried a hard-wired video test direct to the head-unit when I got the camera to prove the connection and function, and it allowed me to have PAL 625 line higher resolution from this “Universal” camera (ie adjustable video standard)
The pictures are excellent, and the Alpine lets me set the parking limits, but I’m not impressed by the camera’s flimsy mounting bracket. Maybe some more metal-work.
Next is to set up the link from this new camera when it is on the boot lid .
I don’t know how much bandwidth I can squeeze through the new RF kit. It’s a leap in the dark, and the wires are not quite as conveniently short as shown in the generic pictures.
Or, I might find a thicker umbilical to allow a video wire.
Or, another idea is some thin video multicore left over from a security camera, but that also would need some more soldering.
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Well, the reversing camera works, does everything claimed for it, and the Alpine setup menus make sense (provided the Parking Brake is On, otherwise hidden), BUT can I now get a picture on the Alpine screen?
No.
Fortunately I tested the camera out of the car, before doing any complicated surgery in trying to mount it for best image.
I simply plugged its yellow output RCA into the Yellow Video Input (actually Alpine Aux2 although I thought it was Aux3) down the yellow wire of the triple RCA-RCA loom I installed. The Alpine switches over to “Rear camera” and puts up the safe parking area markers, but no image. I normalised all the Image settings to midrange, nothing. I even read the Alpine instructions!
So I had a look at the camera output plug with the Picoscope, and sure enough each of the video formats it’s meant to produce seemed to be there when I cycled through on the little push button, as is the 12V “I’m here” signal on the little yellow wire coming back out of the RCA.
All that leaves is a wire between them! I have a horrible feeling that the one broken wire in the system is the AUX1/2 video input right on the new Alpine multi-way plug, next to where I snipped off all the unused wires!
Maybe the head-unit has been in and out of the Dash a few too many times. I used the same trick as the original installer and put a big chunk of gaffer tape to hold in place the wires from those Aux-input and Pre-outs. But I did not wrap a bit of gaffer around each RCA plug join to prevent them walking apart.
All that is left now, before dismantling again, is to put the video into the “Ipod Aux3” jack plug in the cup-holder next to the USB stick, but I will need to find or make up a suitable adaptor lead.
Camera mounting.
I mentioned putting off the immediate camera installation partly because the bracket fitting to the plastic blank plug requires cutting too many bracing webs on the flimsy plastic. I’ll make up my own bracket so holes will miss webs, and go into voids, as with the old camera.
This shows hole positions the new camera might need for a central location and correct field of view; but all the webs are also shown on the masking tape, so the final holes cannot be where the bracket suggested.
To compare, here’s the old camera at a second attempt (earlier holes plugged), and I think I used M3 washers, nuts and bolts.
And how the old Garmin camera looks on the car, with packing washers because the bracket was too short for the lens to clear the edge of the boot lid.
If I can make the new camera talk to the head-unit, I’ll also have to make up a new bracket to adorn the virgin blanking plug I took out of the 25AE.
Sub mounting.
I forgot to take pictures, but I ended up with a very simple idea, made possible by where it is going. One can shake hands through that cubby hole, left arm in through under the lifted deck, right arm in behind the seat. Access is easy even if visibility is less so from under the deck.
I cut some studs from 30mm long M6 bolts, and carefully set them no more than 8mm deep in the back of the sub, each with a lock nut. Studs cut from the 20mm stainless bolts were not long enough to pull everything together.
The multi-way cable came out through an edge-protected hole in the new adapter panel, a bit of gaffer tape was a temporary hold at the top of the panel while I jiggled the two studs through their mounting holes, and added a big M6 penny washer and an M6 nut to each.
And remove the strip of tape.
Seat in my normal driving position and looking down past the headrest there is a gap.
Almost “Flush Mounting” the driver with this clamp sandwiching the trim edge to the cubby hole is a lot more rigid. It has created a pseudo “baffle” and improved the bass response. It nearly doubled the level of its lowest frequencies and produced a smoother response. It is a noticeable improvement on merely sitting loose and resting against the trim as it was yesterday.
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This :~ Mazda MX-5 Miata MK3 NC - Boot trim and reversing camera mount by ianhampton - Thingiverse , and others like it.
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That does look very nice indeed.
And it cannot be misaligned by “helpful” friends trying it as a boot release!
Alas, I have no such modern hi-tech, but I do have suitable traditional measuring tools, chunks of plastic, steel and aluminium, assorted saws, files, drills, taps, paints, etc.
And I’ve sketched out a preliminary design for a neater mounting, I know where the holes have to be, it is only a matter of filling in around them with a suitable bit of solid something, threaded or with nuts!
But there is no point in making it if my head-unit will not accept the video signal. That is the first task to solve. And no great urgency as I still have the old system working with my excellent old Garmin satnav.
I’ve finally put pictures on the Alpine screen.
First I played a DVD, and all that worked as one might expect, proving the monitor knew about PAL 625 video and had good enough audio and video quality.
But using the iPod connector in the centre console proved “interesting” and I learnt a lot about OMTP and CTIA standards for the TRRS mini jack. The iPod socket is CTIA, which is the same as a headset with the video (or microphone) on the Sleeve and the ground on the Ring nearest the Sleeve. But could I find a CTIA wired breakout lead?
No.
But there are countless versions of leads for OMTP where the Tip is video and the Sleeve is ground.
So I made up a ground-swap lead (Signal In to Ground Out and Ground In to Signal Out, AAARRRGGHH) using an off-cut pair of RCA-f leads (from the head unit Pre-Aux socket), and a normal RCA-m to RCA-m patch lead, because of too many female RCAs.
Now the video goes into the breakout’s Red RCA instead of the usual Yellow.
The camera’s 12V came from a normal mains wall-wart.
Pressing the Magic Button on the camera lead stepped through the TV standards. It is upside down as if under the boot lid, and looking at its output picture below shows mirrored PAL, the third step. And I was able to set the quality etc, OK considering it’s indoors under the garage’s fluorescent light.
OK so far.
Snag…
This “Other” camera Aux3 (iPod socket) input cannot be selected for a reverse camera function. And the Aux1 input which can be selected for reverse and tries very hard to show the reverse camera has lost a connection somewhere in the wires I added.
I’ve made progress on the camera inputs but still not seeing it when reverse is selected.
Yesterday I went back to basics before stripping it all down again and simply used a test meter on Ohms to see if there was a 75 Ohm video termination on the end of the yellow Aux In wire, as with the iPod input.
Great Joy! It showed 76 Ohms which is the video term plus a bit of resistance in the cables and test leads. Phew, I don’t have to take out the head-unit.
So before doing anything else, I did what all great engineers do as a final last resort; I Read The Folding Manual from start to finish - a couple of hours last night…
It sets out a complicated hierarchy of circumstances when video can be where and with what connections, so I set up all that and then slept on it.
I had already seen video via the logical name “Aux3” iPod input jack-socket; Reverse merely blanks it.
It seems the logical name “Aux1” is reserved for USB Player(s) input regardless of where it is connected, and as well as playing my music from a stick it does show jpegs from another images-only memory stick, and video from a USB hard-wired phone.
All that is left then is logical name “Aux2”, which can be called by a primary source name selected on the touch screen here USB Player and a secondary source Aux2. Confusing.
And today I now have a picture here on Aux2, so the wires all connect correctly, and Alpine sees the camera.
Selection screen with inset image from Aux2
Grrr! Reverse gear selection is recognised and interrupts any current image as before and shows the markers which can be fiddled with, but no camera.
I’ve now tried all the permutation of inputs except the one buried by the head unit with the five-pin Direct connector for an Alpine camera.
It doesn’t help that if one makes a wrong choice by accident, it sometimes clears down lower steps in that hierarchy to Off or Default, which means starting all over again.
In theory the manual says I can use an Aux input for this, and there are various options to force it, eg setting the Direct as a Front camera and the Aux2 as a Rear camera. Apparently the iPod connector cannot be used as a Rear camera.
But I’m a bit stumped for now. Late lunch.
It’s no good.
I think only the Direct 5-pin plug will allow a connection, and the manual is lying about the Aux input, despite everything switching around as required.
The Aux input shows a beautiful sharp picture on the screen to various source selection labels, but as soon as I release the Handbrake it vanishes “for my safety”, and the Reverse merely puts up the cones on a black background, no video.
I can find any number of 6-pin to RCA adaptors for a couple of pounds, but no 5pin. I might buy a 6Pin and see if I can apply surgery to it as I only need two of the wires connected, much better than hacking the loom cable from the Alpine.
Hmm, they seem to be evaporating too…
Failing that I will have to hack into the loom wires and solder in a yellow RCA directly to this Direct camera lead. The easiest place is near the smaller multiway on the back of the Alpine, although electrically it should be right behind the 5pin socket at the end of the wires.
It occurred to me I could make up a lead, IF I could find the connecting socket.
So I searched my favourite industrial supplier and I think I identified the shell (probably MP013301) and its contacts as Multicomp Pro 2mm, and both apparently in stock.
BIG SNAG - while the shell is mere pennies and available ex-stock as 1-off, the crimp contacts are only available in a full roll of 10,000, for £95 plus VAT. Order over £40 therefore free delivery, but no point.
Scratch that option.
This was the pic of the plug I used as the basis for my search for a mating socket.
