Back in 2003, my headunit had the ERR3 problem and the dealers in France did not want to change it under warranty so I bought a Pioneer headunit from eBay at a very good price. At the same time, I had lots of mods done on the car and one of them was having the roof layed with carbon fiber so the aerial was removed when all this happened. As a result when I installed the Pionner headunit, the tuner was unable to pickup any radio signal.
After a few time, the carbon stuff did not turn out quite well so I removed it and had the roof resprayed but with the aerial hole filled ind. I decided to reconnect the aerial but inside the car, along the rear window, behind the side panel. The radio still did not work unfortunately.
now, a bit more than 4 years later, the Pionner mechanism for the front panel broke down so I decided to go for a new headunit. I had to rewire everything as the previous headunit had no ISO connector so I wired it directly on the standard loom but the new one has ISO connectors so I wired a universal ISO adaptor to the loom after removing everything from the previous headunit. While I was doing it, I realised that there is a antenna wire on the standard loom as there is on the ISO connector. I did not connect this wire on the previous headunit.
Guess what, the radio is now working again! What a knob ... I drove the car for more than 4 years without being able to use the radio just because I did not wire the head unit properly ... I really feel stupid now. Luckily enough I have loads of CDs and the headunit was MP3 capable.