BMW e46, Cars

BMW e46 DIY AUX Input Cable

Problem: I want an AUX MP3 player in my 2003 E46 BMW. However, the current options are either pricey or result in poor quality audio. After a quick search on, I found many semi-complete tutorials on how to MAKE an AUX cord that will plug directly into the BMW factory head unit. Since I was trapped indoors as the rain pelted San Francisco for a solid week — I took out my soldering iron and gave it a go.

Disclaimer: I have been using this setup with my ipods and iphone for a few months with no issues. However, I cannot be held responsible for any damage to your car as each application may vary.


– 22AWG Solid Copper Hookup Wire (3 color pack) – Radioshack $6.59

– 300K Ohm 1W Flameproof Resistor (10pcs) – $0.69

– 0.22uF 100V Polyester Film Capacitor (10pcs) – $1.80

– Rean NYS231BG 3.5mm Stereo Plug (Gold Plug) – $1.16

-Techflex 1/4″ Expandable Sleeving 25ft. Orange – $6.88

– Fan Power Splitter Cable 1F/2M 8″ (x2) (Connectors for stereo unit) – $2.95 each

My 2003 BMW e46 stereo info

Head unit – CD53 E46 (has AUX input in back along with CD changer option)


I reviewed the following info from BMW that shows circuit diagrams, ect.

Let’s get it on.

Here are the parts from

I made my wire about 4-5ft long so I can store the cable/mp3 player in the glove box while also being able to control it from a comfortable driving position.

-Cut 3 equal lengths of wire (~4-5ft)

-Solder them to the 3.5mm plug (I used Red for right channel, Black for left channel, and Green for the ground. Be sure to be consistent on both ends of your wire). Be sure to slide the metal 3.5mm plug cover over wires before soldering.

The wires ready to solder to the plug

– Solder and screw on plug cover

3.5mm plug with cover screwed on

– I then braided (true story) the wires to keep them tight and strengthen the wire.

– I slid the Orange TechFlex wire covering up wire and secured to 3.5mm plug using heatshrink (or electrical tape). The covering should cover most of the 4-5ft of wire you have braided.

– Now comes the exciting part. Soldering the resistor and capacitors on. Review the circuit diagram from the link above so that you can be sure to get the layout correct. Note: The resistor should be on the radio side of the wire.

2 Capacitors on Left and Right channel wires

– I then added the resistor and taped the bundle together.

Here is the finished bundle with loose wire ends for our last connectors

All we are missing are the plugs directly into the radio

-Consult the plug diagram from BMW (above) as to what 3 pins you will need to connect your loose wires to. It is very easy once you look at the pins on the stereo.

Back of my BMW HU

– The connectors that fit directly onto the BMW HU were found at a local shop here in San Francisco. It is essentially a warehouse of computer parts. I gambled and bought these computer fan splitter cables, and they worked perfectly. I needed two of them – one for the top pins, and one for the bottom pins. The store has an online store and the link to the cable is provided.

Complete cable before cutting off male ends

-Test fit the connectors (stack them one on top of the other) on the BMW HU

Test fitting the connectors onto the AUX pins on HU

-Cut off male ends and solder on the right, left, and ground wires from our AUX cable. Be sure to note which pins need to be active by referring to the BMW guide attached.

Connectors clipped, soldered, and ready to go

-The cable is done!! Refer to the many guides on installing the cable that can be found on I ran mine down through the glove box and did not need to cut or drill any holes into the car or glove box.

BMW e46 DIY AUX Input Cable

Finished cable attached to ipod

At home with the tire pressure gauge