[Clarky]

Originally Posted by Redbaron57

After a chronic problem with the "Service 4WD System" alarm it has disappeared for the last few weeks. Only three things are different - I installed a GDE Tune, I fully charged the battery and I connected my AGM auxiliary battery for a trip away. Keith from GDE advised it was not the tune, so that leaves the batteries. This is the second time the problem disappeared after recharging the battery. I suspect that when the battery voltage is low the charging system superimposes a mountain range of spiky voltage on top of the steady battery voltage. The 5V regulator is probably not clever enough to stop some of this rough stuff getting through. When the battery voltage comes-up it buries the mountain range. Then the 5V regulator can maintain a steady output voltage and the signal from the transducer stays where the N23 code wants it. I think the AGM auxiliary battery has a lower resistance than the calcium starting battery and is not subject to the rapid discharges, so it is helping soak-out some of the noise and helping keep the system voltage high (like a capacitor would do). Or I may be entirely wrong (a phenomenon that is not unknown)!

Originally Posted by Wanderer

Personally I think you've pretty well nailed it...What I suspected from the start..The N23 reflash has tighened the tolerances too much.

Pretty much what I was thinking too, just another approach.

Originally Posted by Clarky

To be honest I thought I would have seen a complaint in the telegraph's cars guide by now.

My current train of thought is on the voltage fluctuation that triggers the C140F code.

There is no problem with the wiring (short or broken), I doubt there is an issue with the T/C motor or mine would be ok now after it was replaced.
Cracked circuit board is supposed to be in the T/C motor.

I am toying with the idea of a voltage stabilizer & upgrading the earths/grounds of the Jeep.
For a stable voltage it is imperative that you have a good earth. As far as I can see there is no specific earth to the T/C, an earth wire ran back to the negative battery terminal may help stabilise the voltage fluctuation.

I have just ordered a Pivot Mega Raizin voltage stabilizer
http://pivotjp.com/product/vs-m/vs-m-e.html
http://www.ebay.com.au/itm/NEW-PIVOT...item2581130220
I'm not interested in there claims about this & that, just its ability to smooth out the battery/alternator supply.

I am not saying this is the magical cure to our wows, I'm just experimenting with ideas trying to clean up the 5 volts.

But alas none of this should be necessary if F/C did not take shortcuts on safety

Edit
I have sent my infected FDCM to James, he has a few ideas he wants to try.

but it doesn't change the fact that the update is "not fit for purpose" all it would take even with a second battery is a big power drain like a few days camping or using your winch, if you are in the situation of needing to winch then I dare say you will need 4 Low! the locking out the transfer case is a knee jerk reaction, not a thought out solution to a serious but rare occurrence.
The confidence I once had in my Grand has seriously been eroded because of the N23 update.

We are all lucky C/F don't run the health system' we all would have a pace maker in case you have heart attack