I think the withholding of services such as stop start, hill hold assist etc are related to the cars perception of the battery condition. This is a personal opinion based on experience with a 63 plate 60k 4x4 TA. Last summer, on especially hot days, I'd have the yellow triangle and no stop start (not that it ever works) and hill hold, traction control etc all services that I think rely on electrical power being available. I replaced the battery then and even had the stop start for a while. Then today, as the temperature drops to maybe 0 and the car unused (but locked - therefore alarm draining) the yellow triangle etc is back. Give it a run to the shops to warm up and charge and all is well again. So, I think its all battery voltage/condition related and probably not going to show on the "codes".
Any thoughts out there?
