For weeks now the audio in my E46 convertible was cutting in and out, I incorrectly assumed it was a loose wire. The truth behind this is more focussed on one downfall of the BMW/Range rover audio system.. the BM54 unit…

What is it?

The BM54 is an audio amplifier unit which sits at the heart of the audio system, its job is a bit more advanced then a standard car amplifier. it handles things like:

• TMC – Traffic Message channel
• Radio – Memory, signals
• Car audio amplification/speakers (this is where the main fault lies)

Basically.. without this unit not much of your audio system will work (some might say its the single point of failure on the setup)

What happens?

These units are riddled with faults that can appear at anytime, most common faults are:

• IC Amp Chip failure  – These chips control the audio channels ( all 4) and will take out part of the speakers/eventually all of them.
  • This can also cause sound distortion/funny noises on the channels (such as ticking)
• Loss of power/Not turning on – This will be signified by not having an orange light on the head unit/not being able to use the head units functions.
• Intermittent power – Fully functioning system/sometimes not turning on

So what can be done?

The device itself comes at a premium price.. you have options but not many:

• Ebay/Auction Sites – used units go for north of £300 (and can come with faults)
• Replacement direct from BMW – BMW will sell you a refurbished unit for anywhere between £500-700
• Get repaired/upgraded – This is your most viable and cheapest option (price will vary depending on needs, but no where near as expensive as the above 2 options)

Who can help?

The are loads of people out there offering upgrade and repair services but be careful.. some people see easy money in “soldering together” to repair these units and can cause more harm to your audio system if things go wrong.

When i was looking for a repair upgrade job on my BM54 unit i settled on one company who really impressed me both in quality and in uniqueness.

Cartronics (website)- They are a company based in surrey in the UK (company not one man in a shed with a soldering iron) with full professional soldering/testing facilities. They do a whole range of services including:

• Repair of all BMW audio units, CIC,CCC,ASK, L7 amplifiers Mini HK amplifiers
• In house coding and software updates for ALL BMW models, retrofits for all models upto 2015 cars
• ECU remaps

And much much more..

Mark is a very helpful and professional guy, who kept me updated and the whole unit was turned around in no time at all.

Options?

What people think is that its just a case of fixing the unit and that’s it… but its actually and upgrade in power and in quality.

Originally the IC audio chips are poor quality and run at roughly 20watts per channel with no additional external outputs.

A whole new IC chip setup is soldered in with its own power which can run up to 40watts per channel and is a much higher quality product. here is a pic that Mark was kind enough to send me showing the new board in place:

As you can see i have opted for the additional RCA outputs if i wish to bypass the unit all together and run and external amplifier unit instead:

The difference in sound quality is amazing, you find yourself turning bass down!