G6 ABS Module Failure

Interesting issue. I've seen similar ABS/traction problems on G6 models. When you say 'control unit', are you referring to the ABS module itself, or another module that feeds data to it? Have you scanned for specific fault codes beyond just the general ABS light?

I suspect the ABS module itself. I retrieved fault codes pointing towards implausible speed sensor readings, but the sensors seem to be working. How likely is an internal ABS module malfunction, and is there a reliable way to confirm this before replacing it?

Okay, implausible speed sensor readings point strongly towards an internal ABS module failure. Given the symptoms, it's highly probable that's the issue. Unfortunately, confirming it definitively without specialized equipment is tough. I'd recommend taking it to a reputable workshop to confirm the diagnosis and replace it. I would budget around 1000€ to get the issue solved.

Based on your assessment and further investigation, I replaced the ABS module at a specialized workshop. As you predicted, this fixed the speed signal fault, resolving the ABS and traction control issues. Thanks for steering me in the right direction; your expertise was invaluable.