Ok so today was a really bad day. Our 95 Z28 convertible has been sitting for a while till we could afford to have the head gaskets and some other work done on it. Work done now. Many weeks later we still dont have it smogged and have been going thru a list of things checking them off as we go.

Today we were out and turned on the rear defroster....first time in a looooong time and obviously something electrical (smell) was not happy....so much so that it blew the rear window into many tiny pieces.

Later today we went down to the smog station for hopefully the last one needed and now the computer cant be read. Took it to another mechanic we know and he said the same thing. His machine gets power but no communication.

I am not a mechanic of any real type but would like to know where to start looking because I am guessing we shorted something, lost a ground or blew our computer chip somehow. Does the closed circuit that the defroster provides have to be complete or that is irrelevant? All fuses on drivers side and the ones under the hood seem to be intact.

Help.....anyone...

 

You '95 setup is an OBD2 ALDL cable connector under the dash, but the PCM is OBD1. Normally OBD1 PCM is not scanned as it does not contain any emission ready data. Also there was no industry standard for OBD1 software so the testing facility needs unique software for each make/model. Are you sure the emission facility and your mechanic understand that. Rear window defogger circuit is from Circuit breaker 12 (30 amp) that also feeds the power seats, nothing else in the circuit, it does not go to or power the PCM nor ALDL link. Maybe you blew a fusible link further back, what else does not work besides the rear defogger ??

 

The reason we associated the defroster and the computer that was affected was because about 8 days ago we had an oxygen sensor changed and then went for a smog (failed) and both the mechanic who changed the sensor and the mechanic that ran the smog did not find anything wrong with our cars computer. Nothing else has happened in the interim except for the defroster overheating and blowing out our back window on the morning of the retest. That is why we associated it with some sort of electrical issue.

Anyway we were lucky enough to find a reasonable auto electric guy and it was something under the dash to do with the wiring harness.

Thank you for your helpful comments.