Peugeot 407 Limp Mode ABS Fault

Limp mode on those Peugeots is a proper headache. ABS being a likely culprit is a good shout; a faulty ABS module can definitely throw the CAN bus into chaos and cause consequential faults. Has the ABS light been on at all, even intermittently? Any diagnostic codes being thrown? Specifically looking for anything ABS-related, but honestly, check for everything.

Cheers for the quick reply! No ABS light, strangely. I've got a cheap OBD reader, and it flagged a generic P0700 'Transmission Control System Malfunction'. I'm guessing a proper diagnostic is needed, right? Could a dodgy wheel speed sensor cause this?

P0700 is the classic 'something's wrong with the gearbox, go look elsewhere' code. The fact the ABS light isn't on is interesting, but don't rule it out. Yes, get it hooked up to a proper diagnostic tool that can read Peugeot-specific codes, especially for the ABS and transmission control modules. A dodgy wheel speed sensor could theoretically do it if the ABS system is freaking out and sending bad data to the TCU. Honestly though, at this point, you're chasing shadows. Time to get it to a garage with the right gear.

Thanks for the advice. I took it to my usual workshop, and you were spot on. It was a faulty ABS control module playing havoc with the transmission. They've recoded it, and it seems to be running fine now. Thankfully warranty covered the whole 0€ bill!