Problem pairing again Nexus 5 with Alpine car stereo I had my Alpine radio paired and working with my nexus 5.  Then someone unpaired the device on my phone when they wanted to pair it to a different bluetooth device.  Apparently the Alpine phone passphrase is '0000' (if it is needed - I can't recall it being asked for when I initially paired it and it seems that that is a "default" PIN that is attempted automatically?)

The new device did need a passphrase which was '1234'

I have been trying (unsuccessfully) to re-pair my car stereo with the phone.  The message I get is that pairing was unsuccessful due to an incorrect PIN/passphrase.

I can't find anywhere in setting on how to change the passphrase - because it never asks me for one.  

I am assuming somehow this is a bug and the last successful PIN is being used.

Previously my stereo would prompt if it should allow the pairing and i would select Yes - this time it doesn't work.

I have seen what looks like similar questions/issues on other forums.  It seems to be a bug or at best a horrible hidden configuration somewhere.

To reiterate:


device A was previously paired fine.
device A was unpaired
new pairing to device B with a PIN
no longer able to pair with device A - with an error message of bad PIN/passhphrase but I
never supplied one for this device.


Any pointers or URLs or suggestions would be most appreciated. (aside from resetting to factory)

EDIT:
To answer the questions in a comment:


I have to look up the model number
I cannot attempt to pair using PIN 0000 - the phone does not give me a choice to do so.  I wish it would - in that case I could probably do it.
Same as above
I have turned off the radio - not sure how to disable BT on it - I will try that
Yes - many, many times - as well as shutting down phone
I am pretty sure visibility is on.  It was working fine until then and I will try it with another phone later today - it is visible. The phone discovers it.  Must be on
The message is displayed on the phone.
The issue was not Android.  (Except perhaps the misleading error message.)  

The problem, it turns out, was that the pairings on the radio were "full".  It seems this radio (CDE-133BT) allows 3 pairings.  Well, I inadvertently renamed my Nexus some point along the way when I also unpaired it from the phone.  Attempting to re-pair without first emptying a free slot on the radio failed.  I do not know what the comms is like for denying a connection based on that, but either the radio sent incorrect information about why the pairing was denied or Android reported an incorrect reason.

The problem is solved - By the way  - the way to empty the bluetooth pairings is NOT in the manual - I watched a YouTube video of someone making pairings and discovered a way to find what the pairings were.

Not sure if this Q/A still belongs here, but maybe it will be helpful for someone with an Alpine CDE-133BT someday.