After almost a week of not having the "service 4wd system" coming up, it came up again yesterday. Tried to clear it with OBD JScan, but it would return after ~2 mins of the egine running.
I got hold of BlueDriver and followed the insturctions here
http://www.ausjeepoffroad.com/forum/...d.php?t=142961 with the same result.
Code is C2109 "Drivetrain Supply Voltage Circuit Low".
I can still engage 4lo but when the engine is off and the key is in ignition, then start the engine and drive off. To return ot 4hi, turn off the eninge, turn key to ignition and de-select 4lo, then start the engine and drive off.
I called my local Jeep stealership (Wanneroo) to check for any outstanding recalls, all done, and ask about P73 firmware update, they said it was done in 2017...
My plan now is to:
1. Clean the connectors on the TC motor.
2. Get new batt as I suspect mine is on its last legs anyway.
3. Run through the read and clear codes process again with JScan and BlueDriver (don't need to use both, but why not).
4. Last resort, go and see a dealer and press them about redoing the P73 update (as there's a chance it wasn't done properly before).
5. Last last resort, buy a new TC shift motor.