Ah! The detachable fascia.
Contrary to popular belief, this iss not the only part that retains a code number. The main code number for te unit is stored in the rear, and a corresponding code number is also held in the detachable panel, meaning that the stereo would require the correct fascia to be fitted in order for it to work.
There are many makes of fascia, that all appear to be physically identical and if you look closely at the back of them, they will have the manufacturers name on them. Blaupunkt, Delco, Philips, VDO, Siemens VDO to name the most popular ones.
You must never mix and match manufacturers, ie, a DELCO fascia will not function on a PHILIPS head unit as they are electronically very different inside.
However, if for instance you had a PHILIPS CAR400 with a missing display panel, and you inserted a different PHILIPS panel, it would come up with an error message of PANEL, but if the radio code was correctly entered, then it would reprogram that panel to go with that radio.
As far as miixing and matching fronts with different radio models within the same manufacturer group, I must confess to never having tried it - but my suspicions are that it may well work, providing of course that the fascia in question had the correct button labelling and configuration on the front.
