[RhinoTourer]

The ECU will throw a fit at very low voltage.

My battery failed in August, no response to key when I tried to unlock with the button. Found the battery voltage 'floating' around 9-10v so thought I'll try and start it as didn't want to go looking for leads.

What surprised me was that despite the starter struggling it managed to start, great I thought. Pressing the windows button to confirm all was ok not so great. I can only compare it to pressing the detonate button. All hell let loose, fuel gauge & stereo died, wipers came on then stuck midway, you get the picture.

With the engine running the battery now had a whopping 6v. So thought alternator What to do next? I should have switched it off but as I had it booked in for another master cylinder & radiator with the worlds slowest mechanics (I got it back last week btw !) I drove the bl**dy thing instead and decided I'll fit the spare when I got her back later that day (Ha ha). when I got to the garage I checked it again and it had 5v. At 5v the engine was still running but I had no wipers, no horn, no stereo or indicators

Turned out to just be a U/S battery, all fine once it was swopped out. Didn't even store any fault codes though which given all the low voltages I found very strange indeed.

TLDR if battery drops below 9v ECU/Canbus doesn't like it.