jpurban

Looking for some confirmation...

Will the 997GT3 master cylinder (99735591030) work with the stock 996TT ABS/PSM?

Would love to hear from some folks successfully running both... Thanks in advance!

powdrhound

jpurban

Thanks, powdrhound. You're confirming my suspicion. I've had issues since replacing my stock MC with a 997 version that has 12mm/12mm connection. The code I get is something like 4600 Pressure Sensor, which sets everytime I first exceed 30 mph or so after start-up. I can't remember if it is a GT3 version or not.

I also did a manual bleed on my PSM pump and it would NOT work without slightly depressing the MC. That was a pretty clear sign the MC was incompatible.

This said, I've been driving without PSM/ABS for years now with no issue. The 996TT has so much grip and is so well behaved, I haven't found much need for PSM. I've overcooked some corners... and no snap oversteer like the old 911s... or the current corvettes. ;-)

I'm struggling with replacing my working MC (as a fix to the ABS/PSM error) because the stock MC is pricey at $580 or so AND because I had more issues with PSM enabled than disabled. I have been one of the lucky ones that had the brakes lock up, stranding me on the side of the road. You have to open the bleeder valves to get the car rolling -- or wait for it to cool down, usually overnight. That issue was the reason I changed MC -- I thought the MC circuit had gone bad, not fully releasing pressure. Since the PSM hasn't worked since I replaced the MC, I'm not sure if thr root cause was the old MC or the PSM system.

Anyway, thanks for the response. I'll stew on replacing the MC, returning back to stock, or continuing to live without PSM/ABS.

Just curious... How much work and expense was it for you to convert to the ABS only system (996 Cup version, right?)?

powdrhound

Here is a repost of what I posted a few years back:

It's a 2005 996Cup Motorsport ABS. These are now trading on the used market place (if you can find one) for about $5-6K as they are no longer available new from Porsche MS. Naturally you need to add the cost of labor for the install. The Cup ABS is nothing more than a basic 4 channel 986 Boxster hydraulic unit with a Motorport brain. Physically it looks like any Boxster unit that sells for $150 on Ebay. It's the brain part that you are paying the $5K+ for. The ABS unit is a direct bolt on but you will need a new mounting bracket along with new brake lines that connect the abs to the distributor block. You will also need a Cup brake fluid reservoir. All the parts are about $150 and can be bought from the dealer. I looked up all the part numbers in the 2005 GT3Cup PET.

With that said, this is not an easy (or cheap) mod. While the physical install is simple, the wiring will require someone who has the Cup and TT/GT2/GT3 wiring diagrams with a thorough knowledge and experience doing this type of work. My shop actually discovered some errors in the factory manual regarding the labeling of the respective wheel sensors. The stock ABS connector will need to be completely de-pinned and the correct wires re-pinned into the Cup connector which needs to be purchased separately but it's cheap. The Cup ABS communicates with the instrument cluster over K-line while the street ABS on all GT2/GT3/TTs over CAN bus. As such, while the Cup ABS will be operational, your instrument cluster will not be able to get speed information from the ABS module which means that your speedometer and odometer will not be working. This is not a problem as long as you use a standalone dash display like an Aim or the MoTec I'm using in the pic below. MoTec displays countless selected parameters including speed and odometer information of course (plus you can't see the speedometer anyway with the standalone display ahead of it). We are also feeding the Cup ABS information directly into MoTeC which will display any fault codes if they were to pop up. You might wonder if you could use a Cup cluster but that won't work as it will not be compatible with a lot of other stuff on the street car DME. With the Cup ABS you will loose PSM and the pump and yaw angle sensor and associated wiring can be removed as they serve no purpose. While I've found this one of the best mods I've ever done to my track car, I honestly see no benefit for a street car. Hope that helps.

Ronny Pettersen

I've just done this mod, and see the same p4460 code.
Will disconnecting the psm remove this error? i need the abs to work and the psm/abs lamp to go away to pass inspection.

I see people mentioning the brake light switch and that adjusting this might resolve this error, any thoughts around that?

powdrhound

powdrhound

The only way this works is if you disconnect PSM. You will absolutely positively have a PSM failure code, “PSM failure drive to workshop” message, and a PSM light lit up in the dash. You can clear the PSM failure message with the stalk (it will reappear every 30 minutes along with a ring), the fault code will remain in the ecu memory, and the PSM light will remain lit (no way around it unless you diassemble the instrument cluster and remove the bulb.

Nzo

Is there no way to code this type of thing out in the ecu? These cars have been out a long time, I'm always surprised that something like this isn't an easy software fix.

powdrhound

NO. The coding is actually in the cluster, not the ECU. You would need to completely jailbreak and recode the cluster but I'm not aware of anyone that has ever been successful at that and our local cluster programmer nerd said it would be a major coding feat. Guys can easily recode the mileage but nobody has rewritten the cluster programming itself.

The alternative is to install a GT2 cluster but in order to have a functional fuel gauge you would need to install a GT2/3 fuel tank which would in turn necessitate a complete change out of all the coolant pipes and fuel lines from front to rear.

Nzo

Interesting, I guess the market for this kind of work isn't worth the time invested if thats the case.