Removing factory AMP

[branjb]

Hey all,

I have a 2003 3.0 that I am working on replace the head unit. I've seen other people have success putting an aftermarket head unit in with a DSP system by leaving the OEM head unit in the trunk and splicing the k-bus line from the amp to the head unit.

Trouble is, how do I remove the amp to get to the wiring harness? I've got the metal bar that holds it down off so the amp is loose, but I can't quite figure out how to disconnected the harness from it to get it out. There is almost no wiggle room to fit fingers, tools, or anything else down the side where the harness connects to the amp.

Anyone ever done this?

 

[branjb]

Followup in case anyone else has this question:

It's really easy to do. If you reach down underneath the curved part of the harness, there is a little piece of plastic that you can press in along with a release latch that you press down. This will pop the entire assembly out.

Next question; all of the tiny wires are hidden inside the harness. Anyone have a better way of finding out which wire corresponds to which pin than to splice open wires and continuity test the pin on the harness?

 

[nightyard]

Followup in case anyone else has this question:

It's really easy to do. If you reach down underneath the curved part of the harness, there is a little piece of plastic that you can press in along with a release latch that you press down. This will pop the entire assembly out.

Next question; all of the tiny wires are hidden inside the harness. Anyone have a better way of finding out which wire corresponds to which pin than to splice open wires and continuity test the pin on the harness?

Google z4 amp pin out or what it is

 

[branjb]

Google z4 amp pin out or what it is

I ended up using the harness from the CD Changer instead as it is more accessible. Don't know if anyone is interested in a write up, but I was able to successfully install an aftermarket head unit into a Z4 with DSP by relocating the OEM head unit to the trunk and making the appropriate connections.

A quick summary, if you put the oem head unit in the trunk and connect the IBUS (pin 9), 12V to PHONE MUTE (pin 10), GND (pin 12), and 12V ACC (pin 16), the oem head unit stays in the loop allowing you to connect an aftermarket radio up front and retain the OEM DSP amp / speakers.

 

[NeilP]

Surely it would have been easier (and probably sound better) to just do without the factory headunit and amp altogether and just run an aftermarket amplifier and headunit if you want that?

 

[branjb]

Surely it would have been easier (and probably sound better) to just do without the factory headunit and amp altogether and just run an aftermarket amplifier and headunit if you want that?

It was actually much easier this way. From what I read and what a guy told me in an audio shop, the stock speakers have a non standard resistance that wouldn't work well with an aftermarket amp without risk of blowing them out. That would mean in a traditional sense to replace just the head unit (my oem head unit was starting to have weird issues), the amp and all speakers would have to be replaced as well.

What I did was swapped out the OEM head unit with an aftermarket one using a standard BMW audio harness; that part was plug and play. In order for the OEM amp to work though, the OEM head unit has to be detected on the K/I Bus. I had a lot of trouble finding documentation on how to do this, but once I found everything I need, it was quick and easy.

I found the harness for the TCU in the trunk and all wiring was taken from that. All I had to do in the and was swap out the head unit in the front, then go to the TCU and grab pins for the IBUS, accessory power, and ground. Accessory power was routed to both "12V Direct" and "12V Accessory" pins on the OEM head unit. The I-BUS line was routed to the I-BUS pin on the oem head unit, and ground to ground. That's all that was required in the end to swap out the head unit.