PontiacBonnevilleClub.com

I have an aftermarket stereo in my car, which is apparently causing issues with the ECC. As i look in my shop manual, there is a wiring harness that comes from the back of the stereo and goes to the ECC (dimmer and PCM). There is a purple/white wire, and two dark green ones. The stock stereo has a way of routing the signals to these wires, but the aftermarket one doesn't. Has anyone else encountered this issue, and/or figured out a way to fix it? My cheapo, four year old sony stereo sounds MUCH better than the stock one.

I can provide pictures of both my shop manual and the wires in my dash if needed, but it is a PITA to open the dash, and shouldn't be necessary.

On the 92/93 Bonnevilles, there is only a dimmer signal through there, that when bypassed with an aftermarket stereo causes the ECC to be on full bright at all times, which is no big deal.

Bonnevilles of that vintage do not have any PCM signals going through there. You need to be more specific with your symptoms.

On top of it not dimming, i consistently get the code on my ECC that says "Data line failure - PCM". Also my Haynes manual has two of the wires in the diagram as "PCM data line".

Also, I'm not working on a bonneville. It's my car in my signature, 1993 Buick Park Ave