Hello out there in Radioland!!

Have you heard this one.. I have a HU out of a 2007 Cobalt, that has a bad CD player.. Radio worked fine, and XM/Sirius capable (CAT button, I dont listen to a lot of CDs) thought to put it in my 2002 Blazer, which is OBD-II but has no Class II data bus in it like the Cobalt. Reading Simons post, he grafted the BCM into his harness and OBDII socket, but no specifics.. Where would I wire in a donor BCM to my harness to have the bus "wake up" the radio? I have a Metra harness (radio plugs) so I could plug it into the oem Blazer radio harness, but no data connection.. The 2002 Blazer is ODBII, not UART like his 93 Firebird..

If that wont fly, also thought of just mounting it on the bench in the shop.. Again, as it'* a Class II unit and needs a BCM to read/wake, I'll still have to hit a parts yard, find a comparable car and get the BCM from it, fit it to a 12v supply, take the whole thing to a dealer to burn the VIN of the BCM donor car into the radio to.. Why do all this and not just get a boombox?? I dunno

The newer radios are VIN dependant. If the VIN in the radio does not match the VIN in the BCM, it will not work.

Mike, I know that.. taking it to the dealer to burn the new VIN into the radio will allow it to turn on.. thats what I did with this radio.. the HU that came with the Cobalt was non-RDS/CAT (not XM/Sirius capable). I bought this one (XM-Siruis capable) from a supplier, mounted it, took car to the dealer, he burned the Cobalts VIN into the radio, or rather, burned the radios serial into the Cobalts ODB/BCM for $45. Everything was fine, radio, CD, 6pages of presets, then CD quit working. I swapped the original radio back in so the kid had tunes/CD again. So the new radio (Cat/RDS) is sitting on the bench. I know I have to get it burned for the car, or even the bench. I am trying to find how/where the newer BCM gets wired for the radio to read.

Oh, gotcha!!!

You'd have to find the wiring diagram for that radio and find the wire that says something like "data bus", or serial data, or Class 2 data. Something along those lines.

no worries.. the Metra plug into the radio have the two pink leads coming out that are the Class II data in/out.. The 2007-ish BCM I've got to find (try explaining what I want to do to a part yard guy) will have to get wired in somehow.. and a lead going to the ODBII plug under the dash so the dealer guy can plug in.. where is gets cludged in is what I'm looking for..

hmmm, no edit button.. ok.. I have the wiring hjarness for both the Metra plug (what goes into the radio) and the Blazer harness to-whatever socket (used for aftermarket radio), so hard-wiring-wise, I'm good, I'll have to get a BCM from a later model (Trailblazer, maybe) or Cobalt and "franken-wire" it into the Blazers harness.

On the radio Class2 bus, data goes both ways on the same wire, So, on the radio it would be either wire. Because everything daisy-chains together. I'm sure you already knew that. Sorry, just rambling....

Pin 2 on the OBD2 connector is your class 2 data bus.

interesting, there'* two Class II leads in.out of the radio.. I initially had an idea of burning a VIN number into an EEPROM and wiring it, but it would have to be live.. later model TrailBlazer I'm thinking would be a BCM choice.. if I could cludge it into the '02 Blazer'* harness..

I think the in/out is to support daisy chaining of devices. PCM-BCM-RADIO-Door Module-ABS etc.

daisy-chained line.. yeah, makes sense.. thanks!