Insignia automatic transmission slipping

Hmm, that does sound familiar. I've got an Insignia myself and I had similar symptoms a while back – the slipping transmission and the transmission light were dead giveaways. Have you checked for any undervoltage issues, that's a typical culprit. When was the last time you had it checked properly?

Undervoltage, you say? Interesting. Now that you mention it, the battery has been a bit sluggish lately. But how would that directly affect the transmission? I always thought transmission issues were purely mechanical or fluid-related. Could a weak battery really cause all these shifting problems?

Yep, undervoltage can wreak havoc on the transmission's electronic control unit. These modern cars are so reliant on a stable electrical system; a dip in voltage can cause all sorts of weirdness. My issue turned out to be exactly that – a faulty voltage regulator messing with the transmission. I'd strongly suggest getting it checked out by a workshop; they should be able to diagnose it properly.

Thanks a bunch for the insight! I had the car checked at the workshop, and you nailed it – turns out a drop in voltage was indeed the culprit with the worn out oil as a follow up. New voltage regulator and transmission oil change later, and it's shifting smoothly again. 240€ lighter, but a small price to pay compared to a full transmission rebuild. You saved me a fortune!