Older BMWs are stylish, sporty cars that were once on the cutting edge of automotive technology. However, the audio systems of this era could use a bit of an upgrade now that it's 2014. Most people can't survive on just cassette tapes and CDs these days, so how is it possible to play music using modern devices in a car from 2003 or older?
Step 1: Get on the network
E38 and E39 BMWs use an internal wiring network called I-BUS.
BMW 7-Series 1995-2001
BMW 5-Series 1995-2003
I-BUS lets different electronic devices in the car communicate with each other. (Navigation, television, phone, etc.) In particular, I-BUS is used to control the radio head unit and CD changer from the steering wheel and console controls. If you want to upgrade your old CD changer to something more modern such as an iPod, or even stream music over Bluetooth, you'll need something that ‘talks I-BUS' for your controls to work!
The good news is you can easily find BMW-aware audio players on eBay. These are specifically designed to replace the CD changer and mimic its I-BUS interface, so the front-of-car commands for CD change, skip track, etc., are routed to the new device. The device plugs into the radio module to gain access to the I-BUS as well as the audio lines. I'm using a Yatour YT-M07, which offers a plethora of input possibilities to suit most anyone's portfolio of gadgetry. (Bluetooth, iPod, and SD card, to name a few)
Is it really that easy?
Let's take a step back. If your car is fitted with the high-end DSP amp then you’ll find you get no audio output with this type of device. That’s because with the DSP setup the amp takes a digital optical signal from the CD changer directly, and the analog inputs are ignored. There’s no easy hack around this – if you try to patch into say the cassette or radio audio, you’ll find the controls don’t work – because the head unit knows what audio system is active and what control signals should be passed (via I-BUS) for that mode.
The solution is to add an analog-to-digital convertor (ADC) into the mix, so that the amp can be supplied the digital format data it expects.
Installation
To install all of these goodies, you'll need access to the radio module which is in the trunk underneath the padding. You really have to remove everything to access it properly – CD changer, amp, video module, GPS, etc. A long 10mm socket should cover everything though.
With the new media device in place you'll need to splice into the analog signal wires from it and attach these to the ADC input. Then, find a power source wire for the ADC. There are a few places you can tap it from but as my car was pre-wired for the phone module I tapped it from that unused connector. This also meant it was on its own fuse in case anything went wrong.
You can Google the exact phone connector pinout – but brown and pink are what you need!
With the ADC powered up everything works perfectly! Sound quality is absolutely fantastic through the DSP amp and volume/song select controls work as expected. On most audio input devices such as the Yatour, the 6CD changer selection buttons on your BMW radio now map to 6 different folder groups of MP3s. Finally, the cassette adapter can rest in peace.
