ABS PSM Code 4266 Return Pump Fault

Hi all, I was on track with my 996 and suddenly locked up my front left wheel under hard braking. Little butt puckering at 130mph down the straight. I saw the ABS / PSM lights on the dash. It seems like when the PSM activates too many times, it triggers the code 4266 return pump fault and shuts down the whole system, at least that is my theory. This is the second time this has happened, last track day these lights came on, but I was able to clear them the next day and the car was fine. However, when I tried clearing it this time, the lights came right back on. I will try again tomorrow to clear them, but would like to find the root cause of this, especially since it is happening only on track and it is not the first time. I did a little reading, and it seems like when the ABS shuts off the 996's brake bias is completely off? Can I just unplug something to disable the system or is pressing the PSM button enough?

I had this problem and had to replace the ABS pump... My unsubstantiated theory was that driving with the PSM on was killing the ABS pump by overworking it. It was triggering multiple times / lap. I was able to see this through my data logs where the brake pressure would become active when I was at 100% throttle, this was minimized with the PSM button pressed but it was still active. You will have to pull the connector off the return pump to kill PSM fully and while you will have a dash light, the ABS will function as normal. In my experience, the car is un-drivable without a functioning ABS unit. PSM is worthless for track driving anyway so win/win. The price of the replacement ABS unit, even off ebay, not so much win.

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the return pump is where? Is it directly under the master cylinder or is it the the module next to the abs pump? you replaced just the abs unit itself or you had to replace the module as well? Big price difference between the two. I agree with what you are saying about the car being undriveable, the front left wheel locks up much sooner than it should.

The return pump is on the left side of the frunk looking from the front of the car, the error throws a return pump fault but in my cast the actual failure was the ABS module, I replaced the whole thing. Below is what you need to unplug to kill the PSM (return pump).

Ok I am going to limerock in a couple hours but I will try to unplug it now before I leave. My passenger side is missing the fender liner, I wonder if my wheel rubbed through a wire or something since the return pump is on that side.

LR is awesome, have fun. Be careful though, if the ABS unit is intermittent now, unplugging the PSM is not going to resolve that, you need to fix the ABS. So, keep an eye on that ABS idiot light to try to stay out of the grass, or worse. Checking the other associated hardware is certainly a smart thing to do also, good luck.

Thank you. On Monday I was to NJMP Thunderbolt when the ABS went out under a hard braking zone. I ended up in the grass lol. I finished the track day without any more incidents, however, I had much less confidence in my brakes stopping from the straight (130mph).

Cleared the codes and took it around the block. No lights. I then unplugged the return pump. PSM light is on but abs light is off. Going to see how the car does like this. I glimpsed at the wiring and everything looked fine.

Yea so turn off the psm along with unpluging the motor will prevent the psm from screwing with the abs pump but it show a traction control light. Hopefully the abs modual is still good.

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You should be fine. I have disconnected mine. Here is my new PB at LR from the unmuffled day about ten days ago. You Tube