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C33 and CD43 Business Radios

The stock radio for the '97 328iC was the C33 Business Radio, which featured a cassette deck and AM/FM Stereo and weather band. It was a bit underpowered and poor sounding.  A popular upgrade is to switch this out for the CD43 Business radio, which was standard in the '99 and later Z3. The CD43 featured a single disk CD player, AM/FM Stereo, but no weather band. It sounds much better than the old C33, especially if used in conjunction with an after-market amp and high quality speakers.

C33 Business Radio.

TheE36 Business Radio has a few hidden functions that are not documented in the owner's manual. These features can be accessed by turning the key to the accessory position (engine off), turning on the radio, and then holding down the m button on the right side of the radio (this is the button you press to activate manual tuning of the radio - not the Mode button on the left which is for setting the sound mode). Hold the m button for about ten seconds, and the display should change to show the serial number of the radio (it should read SN xxxxxxx, where xxxxxxx is your serial number).
There are four functions that are available. Press the < or > buttons to either side of the m button to cycle between these functions. They are:
  1. Display serial number (SN xxxxxxx).
  2. Display build date (mine reads SV 29-96 18, which I assume is some sort of a date code).
  3. Set speed sensitive volume feature, GAL n, where n is a number 1 through 6. Use the radio preset buttons 1-6 to set the amount of volume change you want at speed. Setting 1 is the smallest change, 6 is the highest. On my car the default setting from the factory was 3, which is fine with me. Some others who drive hard-tops have reported that they like to set this to 1, as the car is so quiet that the speed-sensitive volume adjustment isn't needed. If you drive with the windows down (or top down in my case), you may want to set it to a higher number - try 4 or 5. Then turn the radio OFF to save the settings. Turn it back on, and go for a drive to test it.
  4. Radio station signal strength, freq F nn, where freq is the station frequency and nn is the signal strength. In this mode you can press the 1 or 2 button to tune up or down, or the 3 or 4 button to seek the next station up or down, respectively. For FM stations the signal strength seems to vary from 1 to 15. But for AM, the strongest signal I get is a 5.
Here is some good information on the design of the C33 which help explain some of its "short comings."

CD43 Business Radio

The CD43 Business Radio is a popular after-market upgrade from the standard C33 radio. It was originally offered on the E36 Z3 and M3 coupe in 1999 and later, and also in Range Rover vehicles (during those few years when BMW owned them). You can often find these radios for sale on EBay for about $250.  Many of the ones on EBay were actually originally manufactured for Rover, but have been rebadged with a stick-on "M" label to cover the Rover logo as in the photo above, and then advertised on eBay as original OEM product.  As far as I know, the Rover units and true original BNW units are identical except for badging.
The CD43 features higher power and improved fidelity, especially for the FM tuner. The CD43 features RDS (Radio Data System) and PTY (Program Type) functions. There are two displays on the front – the larger one displays radio station or CD track information, and the smaller indicates the function of the two ‘-‘ keys directly underneath (soft keys). Unlike the old C33, the CD43 does not have a weather band feature. The CD43 uses the I-Bus system just like the older C33 and C43, so it is fully compatible with the optional trunk-mounted multi-disc CD changer. It does not have an AUX input, although like the other I-Bus based systems one can procure after-market interfaces for iPods or other external audio device if you’re willing to lose the CD changer.
Now for a quick rundown on installation and user instructions:


To remove the old stock radio and install the new you will need the special BMW radio tool. These are available from many suppliers, typically for around $15. The mounting screws are located behind two plastic flaps on either side of the radio face.

The installation is a direct plug-and-play replacement for the old radio. The stock cable harness uses a multi-lead connector with a slide locking mechanism. To detach the connector from the old radio, slide the locking mechanism to the side and then the connector lifts off the back of the radio. The antenna connector is a European style coax connector, which is simply a press-fit.

When the radio first powers up you have to enter the security code.  See the Radio Code page for information on how to do this.

Once the radio is on you may have to change its region of operation setting. In my case the radio was pre-set for European operation, so that the AM and FM frequencies and the RDS and PTY functions were not correct for the US market. To change the region of operation, you need to access the radio's Service Mode -- more on that below.

User Instructions

Some of the less obvious features and functions of the CD43 are:
  • My car has the optional trunk-mounted 6-disc CD changer. To access the discs in the external changer, you press the CD button twice. The buttons labeled 1 – 6 are used to select the CD you want to play, and the < and > buttons to select the particular track. You can also choose to play tracks in random order by selecting the “RND” soft key.
  • The RDS (Radio Data System) feature allows the radio to display information that the station broadcasts on a sub-carrier of the FM signal, typically showing the station ID, song title, and artist. Press the button under the RDS indicator to control whether RDS is activated; an asterisk is displayed next to the “RDS” in the display when the feature is active.   Here is some ggod background information on RDS : Wikipedia.
  • PTY is a second type of data stream that displays the type of program – news, sports, weather, etc.  Press the PTY soft button to control whether it is active or not.  This feature is availabe when the area of operation is set to US, but in my experience few stations actually broadcast PTY data.
  • TP is "Traffic Programme," available if the radio is set to Europe area of operation.  This feature causes the radio to automatically tune to traffic reports.
  • Setting station presets: in AM or FM mode tune to the station you want using the < and > buttons. Pressing these buttons will cause the radio to tune to the next station with a relatively strong signal. If you want to manually tune to a particular frequency, first press the “m” button and then the < or > button. Once you have tuned in a station that you want to store in memory, press and hold one of the station preset buttons for about 5 seconds. There are three sets of FM band presets and two for the AM band. The radio can also automatically select the strongest six stations by selecting the “FMA” or “AMA” bands and then using the SCAN function.
The procedure for putting the radio into Service Mode is as follows:
  1. Turn the radio on, and within the next few seconds press and hold the "m" button for about 10 seconds, and the radio's serial number should appear on the display. The unit is now in Service Mode.
  2. Use the ‘+’ and ‘-‘ keys to scroll through the various service functions, as described below.
  3. To change a value, use the radio station preset buttons.
  4. When done, turn the radio off to store your changes.
The Service Mode functions are:
  1. GI nn: Not sure what this is - mine reads GI 48.
  2. GAL n: this is the speed-sensitive loudness feature, which adjusts the volume automatically with the speed of the car. The value of the GAL function can be set between 1 and 6, where 6 causes the greatest change of volume with speed and 1 no change of volume. The default setting is 3, which seems to work fine.
  3. Radio station signal strength: displays freq nn nn where freq is the station frequency and nn is the signal strength. In this mode you can use the AM, FM, and tuning functions to select radio stations and see their relative signal strength. Two values are displayed for FM stations and one value is displayed for AM.  The values for signal strength seem to range from 1 to 15.  I think that these values are used in selecting the strongest stations that are automatically set in the FMA and AMA bands.
  4. DSPn and Vnn: I suspect that this has to do with an external DSP unit that was available on some other cars of the era such as the E38 7-series. In my case the values are all 0 and can not be changed.
  5. Pixel display test: press the 1 button and the display is blank, 2 turns on half the pixels, 3 turns on the other half of the pixels, and 4 turns them all on.
  6. Area of Operation: adjusts the AM band, FM band, RDS, and PTY/TP functions for your particular region of the world. Choices include:

    - Europe
    - USA
    - Canada
    - OC + RDS (Oceana)?
    - Japan
    - No Area

    Press the “1” button to cycle through the various choices. A word of caution: I have found that if you save a different region you will lose all your radio station pre-sets.
  7. View: appears to affect the bightness of the display.  1 = medium, 2 = dim, 3 = bright, 4 = bright (not sure what the difference between 3 and 4 is).
  8. AF: press 1 to cycle betwen AF OFF and AF MAN.  Not sure what this function is.