Astra Transmission Issues

Sounds like a pressure switch issue alright. Have you checked your gearbox oil level? Low oil level can cause the pressure sensor to throw errors and lead to those symptoms. Is it shifting uncleanly all the time, or just when the light is on?

I haven't checked the oil level yet, to be honest. I'll get on that. But if the oil is low, would that really cause all those problems at once? The light, the slipping, the grinding... it seems like a lot for just low oil.

Aye, low oil can definitely cause all those symptoms. The pressure sensor needs adequate oil to function correctly. Low oil means low pressure, hence the error. Slipping and grinding are common with low oil because the gears aren't getting properly lubricated. Still, you should probably take it to a workshop.

Cheers. I checked the gearbox oil, and you were spot on – it was way low. Topped it up, and most of the problems went away, but there was still something wrong. Took it to a mechanic in the end, the pressure switch was indeed faulty and they replaced it. Cost me about 365€. Thanks for the help!