'01 996 PCM1 No Amp - new head unit adaptor harness?

Hi all, have finally bitten the bullet and am going to replace my PCM1 unit in my 2001 996 with the basic speaker package (no amp), but am struggling to find an adaptor harness to connect the new (Pioneer) head unit to the standard, non-amped, wiring? I think I need an adaptor that fits plug A and B and possibly an adaptor for the antenna, but can anyone in the know please let me know what I need and if possible, where to get it? Thanks! :thumb:

I did a quick search and come up with this .. i think its what you need but see what you think ..... http://www.nexxia.co.uk/products.asp?s=Harness Adaptor&c=Porsche ISO radio Harness Adaptors

Thanks for taking the time to search for it, but unfortunately I don't think that's the right one. The blurb says: "Compatible with: Porsche 911 Oct-97 - Mar-03 With 10-speaker system" The non amplified speaker set up on the 996.1 only has 4 speakers (6 if you include the integrated tweeters on the dash units), there are two options with more speakers but they are both amplified and as such use a different plug (Plug C) to get the line out signals to the amp, as I understand it.

If your car has an amplifier and you are not useing it with the new unit then the speaker wires will need running to the head unit to connect them , if it doesnt have an amp then the speaker wires will be there and just need connecting. Green,green black ... purple , purple black etc are the speaker wires , the radio needs the usual feed wires which an ISO plug can be used or just wired direct to the radio. Ive got a feeling that there might not be a direct plug that will just convert 1 system to the other but without looking or pictures i cant say. If you want to take pictures of the wireing and what you are connecting i might be able to talk you through what to conect and where if it helps. I would suggest visiting your local radio shop and ask if there is a convertor as they are the experts. One other site i found had a lot of connectors on it , you may have seen it already but worth a look. https://incartec.co.uk/Cars/Porsche.aspx

I took a shot at one of the amped systems harnesses on Ebay and it arrived today, seems like it might work as it has 3 sockets for the 3 plugs that can go into the back of the original Porsche (Becker) headunit, including the Plug B, which is only used for non-amped speaker line outs. Seems that those speaker line outs, plus the speaker line outs from the other plug for amped versions are routed from the car's harness through a PCB (covered in heat shrink) and then exit as one set of wires into the ISO male plug, which is then connected to the new head unit. I'm hoping that the PCB is designed to send the signal from the head unit to both the amped and non-amped speaker signal wire plugs and so my search is over - this harness will suit both amped and non-amped versions. The Plug B socket is the Brown one in the pic below.

Are you sure you need a harness? When I removed my PCM1 (albeit with Bose), the cars loom had the standard black and brown plugs (with the brown plug expecting amplified speaker feeds). See http://911uk.com/viewtopic.php?p=1141940&highlight=#1141940 . Weirdly, the bose amplifier takes an amplified output from the PCM1 and then amplifies it again. So the PCM1 head unit-Car Loom connections were totally standard - I just plugged the new head unit in. The only 'harness' I needed was an extra single wire (within plug C) to switch the bose amp on - which you wont need if you don't have an amp. I suspect the heat-shrunk PCB in your picture is to convert an amplified speaker feed from the brown plug/head unit, into an unamplified speaker feed to the red plug/amp. If you don't have an amp, it could be a red-herring.

Quotes source post: 1141940

That's good info, thanks. I'm not sure about what I need at all! You can see in the image that there are three sockets to fit 3 plugs from the car's loom. However, the brown one, (Plug B on the oem loom) is only ever used on the basic set up without the amp, that plug is totally redundant if you have an amp, as I understand it? All the wires from that brown socket go directly to the brown ISO plug with the same pin positions, so it looks like you could well be right - no harness is needed for the non-amped speaker wires. The red socket is for Plug C I, which takes the speaker signal from set ups with an amp and takes it through the PCB and to the new head unit using the same brown ISO plug as above (there are two wires going into some of the brown ISO plug pins, one from Plug B and one from Plug C). So, it looks to me like the cable can do both an amped and non amped set up! I guess there's only one way to find out though - I've gathered pretty much all the bits after ordering the head unit last week, but unfortunately the head unit is the only item that hasn't arrived yet! I've already been out in the car pulling various bits out getting ready for the install.

One more query - I want to use the amp signal wire from the head unit to turn on an active underseat sub that I'm going to stick in to add some much need bass. For that I'll need to use the Plug A (black plug) of the harness as my car's loom obviously doesn't have an amp signal wire. However, looking at Plug A on the harness (the black one) the yellow and red (switched live and permanent live?) seem to have their positions swapped in the plug and socket. Is this going to cause me issues with the power supply to the head unit either being on all the time or not on when I need it?

For switching the amp on, your new head unit should provide a dedicated wire (probably blue/white), so don't think you'd need to use plug A. In terms of the harness swapping the constant and switch 12v, I've read on the interwebs that Audi and Porsche have a habit of swapping them in the loom, so they don't match the standard ISO pinout. However, on my 2002 996, this wasn't the case. The loom used: - Black/Red (thick wire): Constant 12V: Pin 4 - Orange (thin wire): Switched 12V: Pin 7 So, if your loom is the same as mine, the harness would mess things up a bit, and you might end up losing settings/radio stations when you switch the ignition off. If you have a multimeter though, its easy enough to check once the PCM1 is out. I notice your loom also doesn't support a wire for speed-dependant volume control, which my car loom supports on pin 1. Ive attached the notes/photos of my cars loom for reference. I'm still guessing you wont need a harness!

That's great, thanks for posting up the guide. I'm thinking I don't need a harness for the speakers, but as you say, I need a dedicated (blue white) "antenna power" wire (essentially a switched 12v live as far as I can tell), which is provided on the black plug harness. It's the blue wire you can see on the pic above - two wires actually come out of the head unit end, one continues into the socket on the harness, the other I'm going to use to turn the active sub on.

OK chaps, started fitting it all today. Will post up pics when it's all done, but it looks great and the sound is a different league to the sound of the original basic speaker/PCM1 set up. It actually sounds like the car has a decent stereo now as opposed to a tin pot half-assed attempt at a stereo! :thumb: A few tips: Plug A and Plug B are a direct fit into the harness that came with my Pioneer unit, you don't need any adaptor harness(es) unless you want to add additional speakers/powered accessories and don't want to cut the oem or Pioneer cables. Possible exception to that is the handbrake signal cable, which is supposed to stop you watching videos etc whilst the car is moving (distracts driver). Most people just connect this to ground, but you're going to need to find a place to attach/splice this in regardless. I used the Plug A harness above, initially so I could splice in an active underseat sub, but meant I could splice in the handbrake signal to ground too. :thumb:. The harness I bought (pictured above) had the switched and permanent live swapped on one end for some reason, but I had to swap them back to their original positions to get everything working properly.

OK, so the sun was shining and the fascia still needs a little attention, but it's all connected, working and looking pretty good so far...

Looks great! I diligently squirreled my old PCM1/Satnav Drive/CD Changer away, but cant imagine what horrible sequence of events would ever lead to my reinstalling them.

I could be tempted to put it back to standard if I sold the car as it would only take an hour at most, but you're right, the basic stereo set up is so poor, I'd never consider it otherwise.

On mine, the speakers are connoted via the yellow block, which on this picture doesn't have anything on. Guessing because its using the brine plug and the blue/green plugs for amp?