PSM/ABS warnings - Need Help
 

I have a problem that started happening shortly after I purchased my 2003 Carrera 4S. I had the car about a week and decided to take a friend for a "ride" in my new toy. I took it up to about 100mph and then hit the brakes.

I got an ABS and PSM failure warning light. When I turn the key off it resets. When I crank the car up and drive it the lights stays off for about 1/2 mile and then comes on. It may come on almost immediately upon starting driving, or it may go for miles. This is crazy.

I have searched the internet and found a lot of potential causes, but no solution.

I have installed a new MAF sensor
Had the battery professionally tested - ok
Had the alternator professionally tested - ok
Cleaned all four wheel speed sensors
Replaced the brake switch and verified that it is working correctly

My car has been modified with a 3.8 liter cup engine, 20" wheels with the correct tire diameter. It also has a K&N filtercharger system. It has a complete Fabspeed exhaust system with no cats installed, so I am getting bank 1 &2 oxygen sensor codes. The ECU has been programmed by Fabspeed. The engine runs smooth as silk until the lights pop on, and then it seems that the car goes into a limp home mode... After this the engine loses power and does not run smooth.

My code reader does not pick up any codes other than the Oxygen sensor codes so I took it to Hendrick Porsche in Charlotte. They suggested that it could have been due to the MAF sensor, but because of the other modifications they were not certain.

Any ideas? Love the car but I am at wits end...

ABS/PSM would indicate a brake problem. Take it to a Auto Zone or someplace that can read the codes. I would think to also check the brake pads and roters, this could be an indication they need to be changed.
Also, this indicates your ABS is not working correctly so under braking there will be possibly no adjustments to the wheels, this is most likely why you go into limp home mode.

Psm/abs
 

I had same problem. Replaced brake light switch with new OEM. Problem solved.

I have ordered one, and will pick it up in the morning. I'll post up my results. Thanks.

This morning I installed a new, genuine Porsche, brake switch. No change. The PSM / ABS lights come on as soon as I hit about 14 -16MPH.

I am thinking about buying a wheel speed sensor and swapping it into each corner followed by a test ride. Maybe one of them will be bad. Is this a good idea? Any other suggestions?

Thanks

OK, here is my take. First off, if the cat bypass pipes were installed thinking through to the logical conclusion the Fabspeed 90 Degree 02 Spacers would have also been installed which would eliminate the CEL as you are getting. Suggestion, have them installed, $150 for the set.
Take it to an indy or the dealer, you have a problem with your breaking system, possibly bad fluid, pads and roters need replacement. Don't mess with this.
Just so you know, the break pads and roters are designed to be replace at the same time, you should not replace one or the other, which I suspect may be the case here.

Jim

Your best chance is to hook it up to a Durametric (or similiar) tool. I have the same problem, and have been doing research on the problem for a while. Replaced the brake switch and nothing. Cleaned all the sensors, and nothing. I'm hoping that the durametric will tell me which sensor is messed up, because I heard that the wheel sensor wires sometimes break or lose connection which causes the lights…I'll try to get under the car this week and let you know.

My new wheel speed sensor will arrive tomorrow. I'll swap it into each corner starting at the right front, and post up what I find. Good luck with yours...

I swapped the wheel speed sensor into each corner. No change...


It seems that when the engine is cold it runs rough and the PSM/ABS lights come on almost immediately upon starting to drive. After the engine comes up to temperature it may go several miles before the warning lights start going off.

I'm starting to buy into the idea that the problem is with something besides the actual ABS or PSM systems. I'm getting desperate. Any other ideas?

1. Get Durametric, read codes and post them here. It's cost is peanuts compared to time you spend wondering your problems and finding shops with inferior one-cable-fits-all OBD readers. ( My guess is P5525, Torque transmission from the DME disturbed at times...)
2. Before that replace that K&N with OEM airfilter. Only problem with this is that after the change you should get all previous codes cleared...depending of the origin just removing the cause (or disconnecting the battery) doesn't remove the CEL.
Use MAF clener before starting the car again.
3. Are you definitely sure that the Motronic really has correct programming for removed cats, ie it ignores secondary O2 sensors?? Or for that 3.8l Cup engine..which Motronic does your car have? OEM 4S or something else? Programmed by whom?

One, but quite far fetched possibility is that your rate-of-turn sensor has gone bad. (P4420, Rate-of-turn sensor) For detecting that you need Durametric or OEM Porsche workshop equipment (=PIWIS).

Remember that when you have ABS/PSM on you really do not have those electronic aids at all...they're totally disconnected.

I was going to order a durametric but the problem is that I am a Mac user. I will have to borrow a PC to be able to run the durametric.

Any other options out there for a Mac?

Finally got the Durametric and have the following codes:

5525 Incorrect Data Transfer DME Master Control Unit
4440 Steering Angle Sensor

I have preformed the steering sensor calibration procedure per the instructions. No change. Is there any way to test the actual steering angle sensor? Where is it located and what does it look like?

Any ideas of the next step?

Removed the K&N air filter assembly and installed an European GT3 airbox. The 5525 code has disappeared, but I am still getting the 4440 Code and the ABS/PSM warning still comes on.

What is involved with changing the steering angle sensor?

Sorry for your problems but thats what you risk when you buy an over modded or radically altered 911.. They may look very cool but 'Mess too much with them and they will mess right back at you'. The PO had his fun over modding and now you pay the price. Hey thats OIMHO but it needed to be said to protect other prospective 996 buyers who are reading these pages. Run away from a modded up car in preferance to a stock 996 and again thats OIMHO... 20inch wheels???? 3.8ltr engine?????? God Almighty.. thats enough.....that says it all....

The 20" wheel/tire combination that is on the car has the same diameter as stock. What is the problem with this? The 3.8L engine is a Porsche crate engine.

Yes the car is modified, but I am getting the same codes as many non-modified 911's that have posted up with the same problem.

I am a first time Porsche owner that is asking for help. You are apparently an angry old man that has nothing better to do than run your mouth. If it is so important that you inform potential buyers about the horrors of buying modified vehicles, then make your own thread.