OK now I'm properly stumped
- In addition to what I posted above, I have now tested the pin 8 earth at the back of the head unit. Continuity to the body earth is sound. My tester beeps, although it does show about 4 ohms resistance between the black pin 8 wire and the body earth I tested it across (a door hinge bolt!).
- Eventually located that D001 front <> dashboard connector, disconnected, cleaned it, tested it (11.8v on pin 37 confirmed), reconnected it and about 11.8v now showing at the white ISO plug that feeds the back of the stereo
I then thought "Bingo!" that should have sorted it. Reconnected the head unit (which I have previously bench tested with a 12v transformer to pins 4 (+) and 8 (-) which fires up fine into CANCHECK mode once you press the power button) and.......nadda, zilch. No power on.
This is really doing my swede in now
There are 3 additional connections in that ISO power bock which I presume to be be the two Can bus lines Can-A and Can-B, and the "Booster Det" line which activates the Bose amp in the boot. Incidentally Can-A (pin3) line is actually also showing as constant +12v when voltmetered across that pin and the earth (pin8). No idea if it should be like that or not!
My current thinking after much headscratching is the body computer has disabled or errored that radio "node" on the CANBUS from when the unit was faulting a few months back, switching on and off randomly (which looks like it was due to lack of vaultage from the faulty connector (pin37) on that front<>dash wiring loom connector). Is that a possibility?? I'm clutching at straws here now 'cos to my mind the bloody thing should be working now!
Anyone else got any good ideas for me to try??
I was thinking of temporarily running another earth and another +12v live to the ISO connector just to eliminate that wiring as the issue - but I'll probaly need to visit halfords to pick up an extortionate ISO block / converter thingy that I can hack into without destroying the one on the end of the wiring loom, and I can also test disconnecting the can bus wires to see if they really are preventing the head unit from powering up now. I know the CanBus is involved in doing some of the more technical shenannigans on the head unit like controlling the button illumination, exchanging codes with the body computer, and displaying the radio stuff on the dashboard LED
My only other options I can think of is trying my local dealer or specialist - but I'm thinking they won't have much experience of testing / diagnosing audio equipment faults, especially this Bose version.
The only ICE specialists I know of in the area (Cardiff) are Uplands Car Radios, but I have no idea of their skills or reputation when dealing with Brera / Bose setups
Why is nothing ever simple?? As always, I appreciate the help from you guys - and hope someone has an idea I can try next.