First time here and hope someone can help. I have a 2004 Grand Cherokee with the standard A/C..... not ATC. The air blows cold until I turn the headlights on. It then goes to full heat mode. Turn the headlights off and it goes cold. If I dim the dash lights, the dimmer they get, the less heat comes out, but not full cold. I bought a set of factory service manuals and studied the schematic. From the Body Control Module, there is panel light driver (it appears) that goes into the manual temperature control. On a guess.... I unhooked the negative battery cable for an hour, reinstalled it and everything worked right for 2 days. I am suspecting it is a problem in the BCM. Any ideas? Also.... if it is the BCM...... and I get one with same part number from a wrecking yard.... (they are $1000.00 from Jeep).... will there be a programming issue and is the vehicle mileage stored there? I know this is asking a lot but any help would be appreciated.

 

I have ordered a BCM off of ebay.... But have yet to recieve it.

 

Yes, the odometer memory is held in the BCM and needs to be programmed to respond to the PCM. This must be done at a dealer with a DRB III scan tool.

Everything today is integrated on the PCI data bus system. Nothing is simple anymore. All the data that shows on the dash gauges is transmitted by the PCM, not by the individual sensors. Even the fuel gauge, for crap sake!

 

Thanks....... that's what I was afraid of. I received the BCM in the mail today. Maybe it is useless for me to change it out.

What are your ideas?

What problems do you foresee happening other than the odometer reading?

And if install it...... and it doesn't work, can I reinstall my original with no problems?

 

IDK. I'm not an electronic genius, just a keyboard flogger like most of us! LOL! Maybe you should talk to a dealer service dept and see if they can reprogram yours or if the new one will be compatible. The only problem with that is they'll probably want to do a complete system diagnosis which costs $100.

Anything that disturbs the data bus can be a problem. For instance, I pulled the fuses on my ABS system in an attempt to eliminate it locking up on a downhill stop on ice when I was just barely rolling. I'd slide about 5 ft past a mailbox instead of stopping at it. The VIC started giving me this message, "Memory seats disabled, seat belt engaged." I don't have memory seats and the seat belt wasn't engaged. The BCM for some reason decided that's what the problem was. I put the fuses back in and haven't seen that message since. Go figure.

 

Thanks...... I will check into it.......