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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.
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.
Loren, thanks for the quick reply. My front circuit bleeds just fine thru the block... Flow at V, VL, VR as well as both front calipers, but I'm getting nothing from the rear outlets ( HL & HR). I've removed the input line from port H and verified there is fluid in the ABS block. Master cylinder was replaced and is now working as it should. New MC was bench bled before installation along with inlet tubes to minimize any air entering the ABS.. MC was replaced because rear circuit wasn't flowing, which might explain why the EBD would have closed the rear circuit (sensed low pressure and closed circuit to protect against a downstream leak). Seems plausible anyway... That is why I'm wondering if I need to reset the PSM/ABS to return the "normally open" EV rear outlet valves to their "normally open" state, which would allow me to bleed conventionally (as you suggest). Most of this is pure hypothesis... Since very little info is available on the Bosch ABS/PSM (I have the workshop/diagnostic manual), I'm left guessing. I have a Durametric, but it doesn't have drive links for individual EV/AV valves -- only the switchover valves. So, I don't think Durametric will be useful in "resetting" the ABS.
Running into some trouble trying to bleed my rear brakes and I've isolated the issue, but don't know how to resolve it. Hoping someone here more familiar with the PSM module might be able to help. Issue: I'm using a Motive bleeder and have good flow into the "H" (rear) input port of the ABS block, but I have no flow from either the HL (rear left) or HR (rear right) output ports of the ABS block. I know the PSM system doesn't have a mechanical proportioning valve, but could the system have electronically isolated the rear circuit? If so, any idea how I might reset it? That could be the wrong track... maybe I have a bad relay or solenoid.