C4 Automatic Transmission Erratic Shifting

Sounds rough! When the trans indicator lights up and it goes into limp mode, that screams electrical issue to me, possibly undervoltage. Modern autos are super sensitive. Have you had the battery checked recently? A weak battery can cause all sorts of weird issues with the TCM. Also, has the transmission fluid ever been changed? Neglecting that can cause slipping and poor performance over time.

Thanks for the quick reply! The battery is relatively new, but I haven't specifically had it tested under load. I'll definitely check that. As for the transmission fluid, I honestly don't think it's ever been changed. Is it possible that simply changing the fluid could resolve the issue, or am I looking at something more serious?

While a fluid change might help a little, I wouldn't get your hopes up too high if it's never been done at that mileage. More likely the undervoltage is the culprit, messing with the solenoids inside the trans. The erratic shifting and limp mode are classic symptoms. Definitely check the battery and charging system first. If that's all good, you're probably looking at a trip to a reputable shop that knows their way around Citroen automatic gearboxes.

You were spot on! It turned out to be a voltage issue. The shop found a bad ground connection causing the undervoltage. They cleaned it up, and the transmission is shifting smoothly again. Cost me 240€ – much better than a new transmission! Thanks for pointing me in the right direction.