Speed Sensor Wiring Harness Problems
For a few months now, I’ve been dealing with intermittent ABS/PSM warnings. As these have become more frequent (ie every time I drove the car), I decided to pull trouble codes with the Durametric. Here’s what I found:
4201 Front right speed sensor - signal implausible. or 4200 Front right speed sensor - op, circ./GND/+ short. 5525 Incorrect data transfer with DME master control unit.
At its worst, I was able to reproduce these codes each time I drove the car and hit a pothole with the right front wheel.
After reading up on these codes here ( https://rennlist.com/forums/996-turbo-forum/750217-abs-psm-and-check-engine-light.html ), I found this is a fairly common issue with lowered vehicles. The speed sensor connects to a harness behind the brake rotor that connects it to the ABS computer inside the car. Over time this harness is ‘tugged’ during extreme steering angles and suspension travel causing the inferior-quality wire inside to break. This is such a common issue that Porsche specifically makes a replacement kit to fix the issue.
I will note that it’s possible the speed sensor is bad, but I easily ruled this out by swapping the driver and passenger side sensor with a result in the same error code on the passenger side. Also, the ABS computer could very rarely be bad in which changing the harness would not remove the error. Also, these codes can appear if the wheel comes off the ground momentarily (ie while entering a sloped driveway), but will disappear shortly after with normal driving.
This is the replacement harness:
I bought the part, 996-612-958-00 from Pelican Parts for $106 shipped. It contains new wires with connector for speed sensor and brake pad wear sensor, as well as wire crimping and heat shrink tubing to cover the connections to prevent water contact.
Installation requires removing the wheel well fender liner, un-attaching the old wiring and cutting the wire under the hood near the battery.
Unhook speed sensor and battery wear sensor:
Remove wheel well fender liner:
Remove plastic panel above wiring and battery to expose wiring, then unwind cloth tape holding wiring together:
Cut the black loom the wires travel through and cut the loom back to expose the wires.
Slide new harness through wheel well - easiest to do wires up from wheel well. Connect harness in place in reverse of how you took it off - this will allow you to know how much extra wire on the new harness to remove once it’s in place (a considerable extra amount is supplied). Splice new harness wires to existing same-colored wires that run through firewall to ABS computer using crimps supplied. Don’t forget to slide heat shrink tubing on one side before crimping wires......
After heat shrink tubing is on, run new cloth tape around all the wires to keep them together and neatly out of the way. I got more cloth tape on Amazon for $5.
Clear the codes if you have a Durametric, or I believe the code will clear after a certain amount of driving once the new wiring is in place.
