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Brian-bmw · #2 05-30-2006, 11:10 AM

You have a very strange set of symptoms, but I am guessing that the dealer's diagnosis is correct. Here is some quick background to help further diagnose. Then I have some more questions and suggestions...

The DSP amp is dependent on the nav computer to operate. It expects to receive control messages from the nav computer, and if it does not see them, the DSP amp will shut itself off after about 30 seconds. However, if you switch the radio off and then back on, you will get audio for another 30 seconds or so, before the amp turns off again. This is typically what you will see in a car when the nav computer has failed.

So, for my first question: is your navigation system original to the car (it should be a MKII version computer and the 4:3 screen)? If not original, is it an upgrade or retrofit? What components do you have?

Next question: Do you ever get sound in the car? For example, if you turn it off and then back on, will it play for about 30 seconds? If so, this points to a dead nav computer.

Normally, when a nav computer fails, you will lose the screen entirely. You may be able to use the radio knob to turn the radio on and off, switch channels, raise and lower volume, etc. But the screen will be dark and none of its functions other menu functions will work at all. (And of course, if you have DSP, the radio will turn off after 30 seconds.) It sounds like your screen is working, but no sound. Is this correct? If so, what menu options are you seeing on your screen?

Last question: are you seeing any other odd symptoms, like turn signals not clicking or flashing on the instrument cluster, while they work outside? Or, is your central locking acting strangely at times?

If you are seeing other odd symptoms with components on the I-Bus, then it could be your car's bettery behind the problem or any other I-Bus component causing problems. Although, on the surface, it sounds like your navigation computer is probably dead.

Try this first. Disconnect your battery's positive and negative cables. Then short them together for about 30 minutes. This will completely reset and reboot the car. (DO THIS WITH THE BATTER TOTALLY DISCONNECTED FROM TEH CAR.) Then, reconnect everything and see if the nav computer and discharge problems continue.

Next, remove the navigation computer from the car. This will not fix the stereo, but if the battery discharge problem goes away, you can probably be confident that the nav computer is the cause. If the car still discharges with the nav computer removed, then your problem is either the battery or another component.

If your battery is original to the car, I would put pretty good odds on the fact that the battery is the cause.

If it is the navigation computer, than you can buy a new (used) one on eBay for probably $200 - $300. Or, you could take this as an opportunity to upgrade to a newer and faster MKIII or MKIV BMW navigation computer for a few dollars more.

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