C5 Automatic Transmission Problems

I own a C5 too, and your description rings a bell. I had similar transmission problems a while back. The erratic shifting and the emergency mode thing sound very familiar. Did you check the transmission oil level, or has it been changed recently?

Thanks! No, I haven't checked the transmission oil level, nor have I had it changed recently. I thought it was a sealed unit. Could low or worn-out transmission oil really cause all these symptoms?

The "sealed unit" thing is a bit of a myth. Citroen doesn't specify a regular change interval, but the oil degrades over time, especially with that many kilometers. My problem was traced back to undervoltage causing the sensors to go haywire, which gave incorrect readings to the transmission control unit, resulting in similar symptoms. Get it checked out by a workshop. They can properly diagnose the issue and check the oil condition.

Thanks so much for the advice! I brought it to a trusted workshop. Turns out, the transmission oil was worn out and causing the issues. They replaced the oil and addressed the undervoltage issue. Now the transmission is shifting smoothly again. The repair cost me about 240€. I appreciate your help!