In reply to a message from Crox sent Fri 14 Sep 2007:
If by ‘CMPU’ you mean the central microprocessor unit, then
it certainly does have something to do with the radio.
When you turn the ignition key to accessory position (I), 12
volts from the radio (14-way white connector pin 4 on a
Light green/black wire) goes to ground through the antenna
logic circuits in the CMPU which control the antenna
operation via the Antenna UP/DOWN relay in relay module K in
I’m quite sure that the installer of your new radio will
have to take account of this.
AFAIK, that small red ‘radio security light’ is merely a
warning to would-be thieves when the ignition is OFF that
the radio has a security code and I do not believe that it
in itself is in any way connected to the CMPU. Replacing the
radio will get rid of that problem - but I suspect that the
existing radio is not getting any power.
Are the blower fans working? If not, suspect relay module H,
the infamous DBC10009 under the passenger side dash in a
Yellow base (or its fuse B2 in the RH fuse box).
Alternatively, check fuse A5 in the LH fuse box.
Either failure would cause the radio not to power up, so the
red security light will continue to flash but the radio head
will not illuminate to allow you to put in the security code.–
The original message included these comments:
I just replaced the CMPU and now the radio security light is lit
(small red one)all the time and the antena won’t operate. I seem to
be totaly locked out of the radio, it won’t even let me enter the
code. My wiper now works (original problem). From what I can tell
the CMPU has nothing to do with the radio? Or am I wrong? Anyway, I
plan to replace the radio in the next week or so… Will this
security thing be a problem for the installer?
Bryan N, '91 Sovereign 4.0 L, RHD
Cambridge, United Kingdom
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