996dailytw

Hello friends,
Sorry if I did not find the same thread in this forum.
My 996.2 Carrera recently has the ABS Light on along with the Brake Distribution Warning right from start-up. Can anyone enlighten me on what might be the cause and the solutions? I am taking it to a shop soon but I would like to first do some research myself.


Thanks ahead for your suggestions

wdb

Codes? Autozone will read them for you as will other parts stores. They won't get Porsche-specific stuff but it would be better than expecting folks to guess.

996dailytw

Hey WDB,
I went to a Porsche Center and the faulty code came out as "4266". They suggest I replace the ABS pump which is quite expensive.
I am not technical expert of the 996 so just speculating: My front right wheel speed sensor was rewired some time ago. Could this be the reason for this fault? Could the sensor be wired incorrectly which caused the ABS to fail?

Thanks again!

ZuffenZeus

IMHO, yes, it could be the ABS speed sensors on the wheels. Personally, if something has been tampered with and you get a DTC, then it is highly suspect in my book. I'd replace and clear the code, then monitor it closely.

I would also advice checking the fluid level. If you replaced with fresh speed sensors and the DTC comes back, then I would make plans to replace the return pump.

996dailytw

thanks!
Could it also be air in the brake system? The air came into the ABS PUMP causing it to fail? I am also thinking about flush the brake system to see if this can fix the issue. Please correct me if my understanding is far off.

ZuffenZeus

IMHO, no harm with flushing the system and purging the system of any air bubbles. I'm no 'expert' in these systems, but I would think air bubbles could cause a fault. Air bubbles are bad news with any hydraulic system. I've just fought this battle while flushing my brakes. Kept getting air in the lines and losing braking. No fun! Scary to say the least. Ended up being a bad master cylinder.

Anyway, flush the system and see how it goes. I would still replace the sensor that was rewired.

996dailytw

hey thanks for the quick response! Yeah I am planning to tackle this issue with both 1)the speed sensor and 2)flushing the brake and get a new set of stainless steel brake lines. If both approaches don’t solve the issue then I will start working on the Pump. At least I will get a the sensor fixed and updated brake lines

thanks again! I will keep you posted~

hardtailer

1. Disconnect all 3 non-manipulated wheel speed sensors and leave the manipulated sensor connected.

2. Start engine, observe the lights in your picture to switch off.

3. Drive away.

2 possible results are

A. The above lights stay off --> your manipulated sensor is not providing a valid signal.

B. Above mentioned lights illuminate as soon as speed reaches 4-6 mph --> manipulated sensor is providing a valid signal.

Result B is not as dependable as A and therefore would require further testing.

Air won't harm the ABS pump or the valves inside the hydraulic unit for that matter.
Brake lines donot play a role in this but if you must, fit them first before bleeding. Otherwise you'll do it twice...

theprf

I think 4266 is the "return pump". This happens because a wire inside the ABS module comes apart. In the USA a company called Module Master can fix this for a couple hundred USD.

wdb

I've used Module Masters. Recommended.

996dailytw

Hey guys I have an update.

It turns out that the ABS module is indeed broken. It was fixed after I sent it to a Module Master equivalent in Taiwan.

While the ABS module was away, I also checked the fusebox and found that my TPMS wiring was connected to the "B9" fuse which is "CU ABS, ASR, PSM" according to the diagram. The car already had the TPMS installed when I bought it so I did not know how it was wired until recently.

Can any expert answer if the additional load on the "B9" fuse is the cause of the ABS module failing in the first place? I am no expert on electrics but I would like to know the root cause.

Anyways, TPMS wire was removed from the fuse before the ABS module was put back. ABS light has not lit up since then.

hardtailer

The extra load by the TPMS did not cause the ABS to fail. Had the load been too high, then the fuse would have blown and even then the ABS would not have been harmed.
Having said that, the ABS is requires a solid, constant power supply and the supply voltage is monitored with the ABS ECU. It could be that connecting the TPMS to the same circuit resulted in less than the required stability of the voltage to the ABS, thereby triggering ABS faults/Amber warning lights.