by Alan Tang 

Editor's note: This article is written for right hand drive models. Left hand drive models may be different.

I have a Japanese spec 98 M2 that came with a BOSE setup. The CD Head Unit is model IM03 and because it is a Japanese spec radio, the frequencies are not compatible with the UK. Hence, the wish to change the Head Unit to one with UK radio frequencies.

Originally I wanted to patch the new Head Unit into the stock BOSE amp and speakers but found so many varying stories saying whether it was possible or not. In the end, I found that it was possible by using a Pre-Amp but at US$150 including a cable harness, it was rather expensive. However, this was not the nail in the coffin for the original project. The final reason why I decided to drop the idea of patching into the stock BOSE setup, was the moisture issue of the BOSE speaker. When they get wet, they seem to have a grating sound at low volumes, akin to the sound of a blown speaker. There was no way I could live with this, as in the UK, the average weather for the year more wet than dry!

So I installed a new Head Unit and speakers and bypassed the BOSE setup completely. I did not need to run new wires into the doors, I just used the existing wiring and patched into the factory loom at the centre console. There are 2 plugs you need to install a new Head Unit and speakers and both are found behind the centre console.

PLUG 1: Is the plug that goes into the BOSE Head Unit.

White/Black is Aerial feed 
Green/Black is BOSE Amp switch (no longer needed) 
Blue/Red is constant live 
Red/Black is Illumination 
Blue/Black is Ignition live

PLUG 2: Is the plug that goes into the BOSE amp behind the heater control unit in the centre console. Gain access to this by taking out the glove box and/or the panel under the steering wheel. The plug is very hard to get to so have patience and plenty of Band Aids ready if you have big hands! 

Yellow/Black(-) and Yellow/Red(+) go to Left Door bass speaker 
Green(-) and Yellow/Green(+) go to Right Door bass speaker

TIP- Double check everything on your model with a tester. Mine is a Japanese RHD model, and LHD models maybe different!

Door panel removal:

1 plastic rivet just below the tweeter. 
2 plastic rivets on the side of the door panel 
1 screw in the door handle lever 
1 screw in the door handle grip 
1 screw in the underneath the felt trim on the door handle grip

Once all removed, just pull on the door panel. Will be quite tight due to the plastic poppers on the door panel itself clipped into the door.

Remove stock BOSE speaker (looks like inverted speaker) and behind them there is a factory plug that goes into the speaker. For some reason, both left and right doors have the same colour wires! 
Yellow/Black(-) & Yellow/Red(+).

Depending on the fitting of the new 8" speaker into the factory hole vacated by the BOSE speaker, you may need to trim the foam covered lip, on the backside of the door panel that used to seal the BOSE speaker, so that the door panel can fit back flush onto the door. (I used 2 Way Co- axial Blaupunkt's and the panel needed trimming)

The sound of the new setup is just as loud and bassy as the stock BOSE setup but the BOSE had the edge on bass control. Depending on the quality and deign of your new 8" speaker, you may want to connect up the stock BOSE tweeter as well to improve sound staging. At a later date I will run an amp to power the Blaupunkts which will hopefully give the bass a bit more control and refinement.

That's all the info you need really. If this is not enough info, then to be honest you should not be tackling this job! Print out this for the wiring colours and let a buddy who has experience (or a pro) do the install.

If you have any questions, email me at 

Back to the Garage

06 November, 2001