Replacing ABS Sensor wiring?

[D_Nyholm]

I'm having problems with my ABS/PASM light coming on and it says it is the right front sensor with a reading out of range. I switched the left front and right front sensors and am still getting the same fault code. My next course of action is going to be to replace the wiring going to to that sensor since i assume there is a break in the wires or a short becuase the car has PSS10's. Looking in the FSM, there is only part numbers for a 'repair kit' that costs about $100. There is also a wiring harness that looks like it goes to the front lights, ABS, and brake wear sensor that is about $350. They are page 414 of the parts catalog. I will try to attach a page.

Has anyone tried to replace this? If so, what parts did you use?

I traced the wiring from the right front and it goes through the firewall and I can't tell where it goes from there. The left front goes through the firewall as well. But the ABS Sensor is in the front trunk. If I got the entire harness, I can't see how I would remove that wiring since it goes into the dash area of the car (i've seen some posts where people remove the dash, i don't think i'd want to attempt that). Does anyone know the routing of the wires?

Last, if it comes to having to replace the ABS computer, is it a simple unplug/plug or would there be much more involved? I'm not worried about having to bleed the system (though I can't hook it to the Porsche computer to cycle the ABS for me, i'd have to do it the old fashioned way). Any places to get this $$$ any cheaper?

Thanks in advance!

[Loren]

Can you please tell us the exact fault code.

ABS/PSM lights can even be caused by a faulty brake light light switch or bad MAF.

[jpflip]

I was going to mention, lately there was a lot of ABS problems related to a faulty brake switch adjustment.....

Brake switch....

Edited March 5, 2011 by jpflip

[D_Nyholm]

The fault code is:

4200 Front right speed sensor

-op. circ./GND/+ short

Like i said, i've swapped the sensors from side to side and still have the same code. I have a Hitachi MAF and it checked out ok. I do not know about the brake light, but they do not seem to be related from what I understand from this fault code. At one time, I got an out of range code, though i do not know what the actual code is as it is no longer stored.

How would you go about replacing the harness? The FSM says to cut it and splice is a new one, but it doesn't give a part number for the new one. What to Porsche Techs do? I'd like it to be insulated with the holders like the original one :)

[Loren]

Fault code 4200

Possible cause of fault

- Short circuit to B+ / ground or open circuit between control unit and speed sensor

- Speed sensor faulty

- Control unit faulty

I sent you a troubleshooting guide via PM.

[D_Nyholm]

Thanks for the help Loren. I went out and ran the tests and it all points to the harness being the culprit. Any idea what my next course of action is? Do either of the parts above seem to be ther correct ones? I know I could just buy the whole harness and then cannibalize it to get that part of the harness, but I feel that would be wasting money. Thank!

[Loren]

Are you sure it is not just a poor connection at one of the connector pins?

[D_Nyholm]

Well, i've taken the plug off numerous times and cleaned it, also pushing it on and off multiple times to clean anything that might be on it. This is over the past 2 years as this problem has been going on for a while. Then of course i've changed the sensor from right to left and the error continued. It is just getting worse and worse. When i got the car 3 years ago, i would get an error once every couple hundred miles. Now it seems that I get it within the first couple of miles of driving the car. Though i did take the car out a month ago after it had been in storage for the entire winter and it took almost 40 miles before it came on.

Would you suggest I put some sort of electrical grease in there to make 100% certain the connection is good?

[Loren]

I am talking about a bad crimp on a connector pin.

[D_Nyholm]

Ahh, i'll take a look at those tomorrow and see what they show. Anything to save me from the $350 harness that i'll have to tear apart! :)

Thanks again!

[silentbob]

Hi Loren,

Could you email me or post the troubleshooting guide as well? My Durametric just pulled the same code.

Thanks!

[Loren]

Hi Loren,

Could you email me or post the troubleshooting guide as well? My Durametric just pulled the same code.

Thanks!

Have you tried the other suggestions posted above?

Many times 996TT's throw an ABS/PSM due to wheel slip - make sure you have given it a chance to clear on it's own if that is the case.

[D_Nyholm]

I forgot to update this thread with the outcome of my problem, but it was the wiring harness that was causing my fault codes. I ordered the 'Repair Kit' showing in the PET diagram above and it is the ENTIRE HARNESS going from the battery box to the wheel with the connectors attached to the end. It comes with everything you need to attach it to your old harness. New crimp connectors, waterproof shrink casing and about 1-2 ft of extra length in case you need it. Went on super smoothly and havent had a fault in about 500 miles or so (I dont drive the car often). Very happy it was not the control unit as that is $$$!!!

[jpflip]

This is a great news . Thanks a lot for sharing the final result and congratulation for the good job!

[RENN 951]

Great info! I keep getting the "brake pad wear sensor" warning light coming on but the sensors are not the issue. Usually happens right after I make the first movement on the steering wheel. I figure it's one or both of those harnesses (different from the ABS harnesses) in the front. It's an annoyance, but I'll have to check into the pricing on the "repair kits" for these harnesses to see if I want to bite the bullet. Other choice is to put some black electrical tape over the warning light on the dash display!

[Karl996]

Reposted in 996 Carrera section

Edited April 14, 2014 by Karl996