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Discussion Starter #1
Hello,
My 12V battery ran dead and the check engine light came on. I cleared them after installing a new battery but code UO16B is still on. "Lost communication to ac compressor control module" and as expected the AC does not work. I checked all fuses. Now I understand that there could be a lose connection in the wire harness going to the AC unit but I already wiggled those. Since this happened exactly when the computer got confused due to the low 12V battery I am convinced it is a computer problem. Is there any way to reset it and to recognize the AC unit? The dealer said it would be very expensive to fix and I am convinced that there is nothing wrong mechanically. Advice much appreciated. Thank you.
 

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Hello,
My 12V battery ran dead and the check engine light came on. I cleared them after installing a new battery but code UO16B is still on. "Lost communication to ac compressor control module" and as expected the AC does not work. I checked all fuses. Now I understand that there could be a lose connection in the wire harness going to the AC unit but I already wiggled those. Since this happened exactly when the computer got confused due to the low 12V battery I am convinced it is a computer problem. Is there any way to reset it and to recognize the AC unit? The dealer said it would be very expensive to fix and I am convinced that there is nothing wrong mechanically. Advice much appreciated. Thank you.
Do you have anything plugged in to the OBDII port?

Most of the instances of U series codes that we've seen have related to something in the OBDII that is forcing the CANBus onto an older, slower protocol.

Reset the codes, unplug OBDII things, and go through a few drive cycles to let it reset.
 

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Nothing plugged in. Interestingly, I did have 2 cheap ass Ebay OBD readers plugged in to get the code. Thank you
 

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Okay so I disconnected the 12 full battery overnight, Hooked it back up and there was hope for a moment. No check engine light on and the remote start(climate control) worked (probably without AC). Shortly thereafter the check engine light was on again and no AC. Bummer!

So is this the way of the future? Where in the age of computerized cars car owners have to take their car to the dealer? And the dealers are laughing all the way to the bank?

But I don't even understand what the dealer would do. They couldn't possibly know. They must have some manuals or some way of getting help with this. And whatever they do, or consult, can I do that also?

Lastly, I remember I tried to jumpstart my vehicle with a lithium ion battery pack and it didn't work and the pack broke down. Is there any other place where fuses possibly are except the engine compartment and the trunk? Is there any other fuse that is somewhere hidden which could have possibly popped? Thanks again everyone
 

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There are additional fuses on either side of the dash when you open the doors. Not sure if any of those are related to AC operation, but might be worth a check before scheduling a service visit.
 

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Discussion Starter #7
I checked all fuses. No avail. Is there anyone else who sees this computerization and the effects on dealers and people's pocketbooks as a problem? Thanks
 

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Since communication was apparently lost with the A/C compressor control module, and assuming there haven't been any damaged wires, it could be a blown fuse (you already checked for that), a loose connector (either power or CANbus) or the module set a 'permanent' fault code when the 12V power went below spec. By 'permanent' fault I mean one which will not clear upon reapplication if in-spec 12V power. If the latter case is what happened, the A/C compressor control module would have to be reloaded with software (along with any updates, if applicable). I wonder if you asked the dealer to specifically reload the module with the latest software, and just give you a price on that, and nothing else, how much it would cost?

I once had a front wheel drive Subaru that started making a growling noise from the rear that I thought was a rear wheel bearing going out. I took it to Subaru dealer 'A', who called back and said I would need a new rear differential and they could do it for $1000. I reminded them my car did not have a rear differential and picked up the car, took it to dealer 'B'. On the way to dealer 'B' I bought a set of two rear wheel bearings at the auto parts store for $40. When I got to dealer 'B', I asked specifically how much to install 2 new rear wheel bearings? They quoted me a price of $40 total. I had them put them in and drove off with the noise completely gone! I guess I could have saved $40 if I had just replaced the bad one, but I figured at that price it was better to replace both as the 'good' one would probably not last much longer.
 

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Discussion Starter #10
awesome story! thanks. so I assume I cannot upload the software myself. This is the new age. After the volt I am going back to older cars. I really mean that. Thanks again
 
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