Can anyone tell me what happens to the car when the 12v battery is disconnected for 5 minutes? I think I want to do this to reset the nav and have it re-read the firmware off the DVD. Has an easier way been found instead of pulling the battery?

I glanced in the owners manual at the fuse box section, but I think there are at least 3 that reference the radio or nav. I tried to pull these, but I don't think the firmware loaded. I may not have waited long enough either.

So, if I just pull 12v power, do we lose the radio presets? How about the trip odometers? Nav presets? Phonebook entries? If you got the 5.1 update from the dealer, what did they do to force a read on the DVD?

I just want to be prepared when I get to this step. Thanks all for the knowledge.

Ray, If it is like my VW, you just get one of the cigar lighter adapers that a 9 volt battery attaches to and plug it into the hot all the time cigar sockets and it holds all the memories. i have done this on my VW many times and it works. Now i am not sure that there is a hot all the time socket, anyone know???

TCH-43mpg
VW TDI--48
08 LS 600 HL-20
08 LX 470-16

My understanding is that the only thing you will lose is the radio presets. Phonebook remains intact. I am not certain about the Nav presets, though. I think those survive too, but I am not sure.

Thanks for all of the replies. I did pull the positive terminal on the 12v battery, and the Nav reset and reloaded as expected. I lost my radio presets, and my previous destinations. I did not lose my trip odometer, or my consumption history, or the nav presets.

Skywagon, Thanks for the mention of the 9v batter to "power port" preset keeper. On the TCH, the ports are switched, so it would be tough to keep radio presets. I'm not sure if this would also confuse the ECM computer. I'd hate for the car to try to startup without the battery for some reason, or for the car to try to charge the 12v battery from the traction battery. Also, I was trying to kill power to the Nav to force a software reload. I just wanted to know what I'd lose from the power loss.

Ray

If I remember correctly, the Repair Manual says that, after disconnecting the 12-V battery, the ICE idle speed needs to be reset. I don't know how far off this might be if it's not reset.

Stan

Stan - Wow!, can you pls double-check? That would be a real bummer, as in: "sorry dude, but changing your [non-std, yes I know that!] 12V battery has become yet another item you're not allowed to do by yourself".

Along with allowing it to go dead. You aren't allowed to do that either!

Per the New Car Options Manual -- the aux battery is "charged by the HV battery module power via the DC/DC converter. It supplies power to the lights audio system, air conditioning system (except the electric converter compressor) and the ECU's." Nowhere did it mention something about the ICE idle speed needing to be reset (in reference to the THS ECU, I guess), however it did mention that the A/C ECU would perform an automatic re-initialization the next time the car is turned on.

Am I missing something?

HybridFan — I checked the Repair Manual, and I'm attaching the relevant pages giving the procedures that require re-initializations to be done. Yes, there is an idle speed setting that should be redone — it's the first one listed in the chart, and the first one in the subsequent detailed descriptions. It's probably not essential to have this redone, but why would they say that it should be redone if they don't consider it desirable to do so? Perhaps the ICE doesn't idle at the optimal speed if it's not reset, and this would potentially degrade fuel efficiency? Maybe someone else would be able to comment on the need/reason for this re-initialization.

Stan

Attached Images

IN_45-66_Initialization.pdf (899.4 KB, 63 views)

Well, that is just great. We can't even replace our own battery without having to hold our left foot up, shake our right hand, and wink five times. What engineer thought that was a good idea?