jpurban

FYI... Powdrhound at 6speed replied to my inquiry... https://rennlist.com/forums/996-turbo-forum/1084729-997gt3-mc-in-996tt-abs-psm-issues.html#post15173164 Looks like the 997 GT3 MC is NOT compatible with the 996 PSM/ABS. At this point, I'm pretty sure that is why my ABS/PSM is throwing the 4600 Pressure sensor error. At some point, I'll go back to the stock MC, which should restore my ABS/PSM, but I'm in no hurry since the 996TT MC doesn't feel great (too spongy) and costs a ridiculous $580 or so. Frankly, I've driven the car for years without PSM/ABS with no fanfare. I daily drive my car in all kinds of Midwest conditions (except when salt/sand is down in the winter) and never had a issue. Even when I (rarely) overcook corners, I get fairly controllable, balanced slides -- no snap oversteer like you'd expect from the old 911s or just about any corvette, old or new. I don't think I'm a great driver or anything along those lines (I've never been on a track) -- I just think the 996TT has an incredible amount of grip and is very well balanced for a rear engine car. The factory set-up just built-in a massive amount of understeer, probably for liability reasons. While I'm still AWD, I've taken out a lot of the understeer tendencies with a stiff rear ARB and disconnected front ARB (I'll eventually reconnect it on full soft). I've also widened the front track (different wheel offsets) and installed wider front tires, while still running 295s in the rear. I run more front (negative) camber -- about equal to the rear -- to dial out understeer and give reasonable tire life (especially in the rear). Still, nothing exciting after years of driving without ABS/PSM. So, I may just continue to live without it... Feel free to reply if you have an opinion to share. I'd love to hear whether anyone has experience different from mine.

Anyone have any experience trying to run the 997GT3 MC (99735591030) alongside the stock 996TT PSM/ABS system? Would love to hear from anyone that encountered problems or success...

Benjamin, If your fault is like mine, every time the car exceeds approximately 30 mph for the 1st time following start, the 4460 error is set. I've read somewhere that the car does a diagnostic test at 30 mph or so. I'm not sure what this diagnostic is testing -- haven't been able to identify. John Update -- My problem was my brake master cylinder. You have to use the stock MC if you want the ABS/PSM to work. Somehow, the OEM internals are special. I used a 997 MC that was operationally equivalent, but the PSM/ABS hated it. Once I switched back to a (new) stock MC, the problem was gone.