AVC-LAN issue with new wiring for aftermarket bluetooth accessory.

Hi all,

This is a cross-post from the Yahoo prius_technical_stuff group. I know a lot of technical folk hang out here too So apologies if you are on the yahoo group and already received this message!

I have run into some problems with my DIY install (on a 2003 Prius) of an aftermarket bluetooth audio device that is designed to be wired in place of a stock toyota CD changer unit.

===PREAMBLE===

To summarise, I have spliced in my device where the CD changer went, but appear to have disrupted the AVC-LAN communications, as I got some VERY angry error messages when I started the car back up - I actually thought I'd killed it.. Now that was panic-inducing..

The device is ebay item 330913283131 (I am not allowed to post links)
Keen viewers will spot that this has the 6+6 pin audio connector (2004 onwards), whereas the CD changer port on the back of the stock head unit has a 5+7 pin configuration.

I noted this before purchasing, and found a pinout diagram, which made me confident that the pins were simply in a different configuration, and that I should be able to buy/make an adapter from the old pin to the new. I was not able to find the 5+7 cable anywhere though.
Instead, I disconnected the harness, cut the wires to the CD changer, and spliced in my new bluetooth unit.

Here's an annotated photograph of the harness after I cut it and rejoined the wires on each cable (see attached image).
As you can see, this is not the typical 'Y-connector'; it was hard-wired into the CD changer.

Here's the pinout information that I found online (the only one I could find) that shows the pins matching 1:1 on the 2003 an 3004 connector (with the exception of the 'TXT' pin, which seems to be an eject pin) - see attached image.

On this paper, that 'TXT' pin is actually labelled as Eject on the connector (pin 11): perens d0t c0m/works/hobbies/ham/prius/avc-lan/avc-lan.pdf

===THE ISSUE===

When I plugged in my new cable, with the BT audio box connected, the car started up normally but the display exhibited the 'lag' problem that seems to indicate AVC-LAN problems (it took a while to switch between displays and beep). I can't remember whether it displayed engine info or not - I think not probably. Don't think the radio worked either, or had weird problems (volume didn't work).

Thinking that perhaps it did not recognise the new CD changer, I disconnected the 12v battery, waited a few minutes, reconnected and turned the ignition back on. This resulted in a triangle with exclamation mark symbol on the dash, and a very ambiguous "BIG PROBLEM" error message on the display - it was a pictogram of a car, a spanner and a battery I think. I think it also said something about the main battery being disconnected or something. Was too panicked to take a pic. Despite the warnings, I was able to start the car and drive it perfectly normally, with no radio controls of course, and with the display only showing the big angry error message.

After changing my pants, I disconnected the battery and waited again and the error message still didn't go away. I was very scared by this point, thinking I'd blown up the display and/or ECU or something, and had to go and have a cup of tea. When I came back and disconnected/reconnected the battery I think (memory hazy) that the error message had gone and the display was just laggy again.

Finally, I unplugged my harness and plugged the cable that was previously going into the harness (from the display???) directly into the back of the radio - ie., bypassing the CD changer completely. Car turned on and everything functioned completely normally, display showed data, radio worked etc.

So that's where I am at now - the spliced-together harness is on my desk and I'm trying to work out what went wrong before I try anything else.

===WHAT I'VE TRIED/CONCLUSIONS===

The first thing I did was double-check that my matching of wire to wire was correct; I rechecked it myself and had a colleague check it also. We both believe that every wire is cabled to the correct one.
I also checked continuity using a multimeter; every wire is OK, none of the connections are bad.

Note that my colleague has an 03 Corolla and I tried my harness and box in his vehicle; it worked PERFECTLY. Therefore, I believe the 'analogue' wiring is correct and OK. My colleague purchased the same device and we were able to hard-wire his into his vehicle's CD changer port successfully, it works faultlessly (had to switch the ACC and BATT pins though, as it kept turning off!)

I therefore have come to the conclusion that this must be an AVC-LAN specific issue, and that the problem is maybe:

1) I need to properly terminate the new device, with a 120 Ohm resistor across the TX+ and TX- pins?
2) I need to flip/switch the TX+ and TX- pins, as perhaps the labelling is relative to the direction (similar to RS-232 DTE/DTS).
3) ..?

I feel like I have exhausted my troubleshooting and research skills. I am hoping someone will be able to tell me where the problem might be, and what I might do to correct it. Given the ANGRY warning messages I got, I am reluctant to plug the harness back in and mess around until I know where I've gone wrong, in case I brick the display or something.

Sincerest thanks for any help,

- Jeremy

 

Hey Chap,

Thanks for the reply.

Your link doesn't seem to work, but did you intend to link to your DICE iPod thread? If so I was just reading it

Very interesting. Definitely seems worth pursuing. Unfortunately I have a cold and am struggling to make sense of all the information.

So you had to cut pin 11, which the perens PDF above says is Eject.. But I don't quite understand how that was crosstalking with TX-? If pin 11 was tied to TX- and Eject, and you snipped it, how is TX- getting back to the bus?

Thanks again for your reply - hopefully tomorrow I can make sense of this..

 

Hmm, doesn't look like it. As you can hopefully see in the attached pic, pin 11 (the prominent grey wire) passes through the 'top' of the Y-adapter, but does not pass through to the bluetooth device..

It looks like, on my harness, all of the wires going from the two arms of the 'Y' are connected, bar the eject and signal ground (I wonder if that's signal ground as in AVC-LAN signal..) - perhaps I should identify the 6 wires you defined as necessary and snip the rest. That should bring my harness up to date with yours, with the exception of the bluetooth end.

BTW, I tried with the extra resistors too that I mentioned in my OP - no difference. After disconnecting the battery and 'rebooting' the car, I did manage to at least get it to say 'external system not available' (or something like that) rather than just doing nothing when I push the 'Disc' button.

Hmm...