THANK YOU VERY MUCH FOR THE SCRIPT!
Worked brilliantly in less than 30 seconds on my Pioneer AVIC-F840BT. I did contact Pioneer and they sent a very, I think, unhelpful email back which I have copied below. Why they think somebody working in a dealership/Halfords (No detriment intended!) is a more secure receptacle for the information than me, a provable and bona-fide Vehicle owner who can supply serials and receipts and has a vested interest in folks NOT knowing how to do this, is way beyond my thought processes.
After all, if someone is going to break into my car to steal the radio, they already have the knowledge to break any password or they are entirely without wit, either way - my radio is gone and my windows are smashed so its a pretty pointless code anyway. Again, many thanks for the info, I am very grateful to you for posting it.
Twain.
Actual Email from Pioneer:
There is a password reset procedure but we cannot give you the details directly as this is security sensitive information which cannot be generally released.
Please take your vehicle to your nearest Pioneer dealership (Halfords etc) who can contact us on 0208 836 3500 (option 1) to speak with one of engineers to perform the procedure. The removal of the headunit will not be required.This takes about 5 - 10 minutes and the dealer representative will need to be left alone in the vehicle during this time to perform the reset.
Details of your nearest dealer can be found from the link below.
http://www.pioneer-car.eu/eur/store-locator
Ring them beforehand to confirm as this isn't a standard service they provide but dealers call us up regularly to talk it through with an engineer so it's normally not a problem.
You will need to present the purchase receipt for the AVH or your DVLA documentation showing you are the registered owner of the vehicle. This is a security requirement necessary for the reset.
