Hi, all! Would like to pick your brain as to what might be going on with my 911 ('99 C2, ~112k miles).

Problem #1: I've owned the car for about a year now, and for the past 6mo+ the ABS and brake wear lights have been illuminated on my dash constantly ever since the harnesses at the front wheels disintegrated while working on the front suspension.

Problem #2 (possibly related to #1): a couple months ago I successfully swapped out my gauge cluster (done for purely aesthetic reasons), but just a couple weeks ago both the speedometer and odometer were no longer functioning. All other gauges--battery voltage, RPM, fuel level, and oil pressure--were and have been working appropriately.

Troubleshoot #1: spliced new wiring harnesses to the front wheels (at the level of the wheels, did NOT remove carpets to re-pin anything) a couple weeks ago, but both ABS and brake wear lights remained illuminated even after resetting them with a non-durametric scan tool. Speedo and Odo still not functioning either.

Troubleshoot #2: swapped in a used ABS pump/module assembly from a dismantler yesterday and bled the brakes. ABS and brake wear lights remain illuminated, speedo and odo still non-functional. HOWEVER, on the drive home the speedo started behaving erraticly--while in 4th gear @ 3k rpm the speedo was fluctuating anywhere between 7mph and 25mph. Additionally, while in neutral the speedo would indicate acceleration when touching the throttle. Odd behavior to say the least!

I have an appointment to drop off the car with my local Indy this upcoming Tuesday, but I'm really scratching my head here and would appreciate a fresh set of eyes. I always thought the ABS and speedo would be linked problems in the 996, but I don't think that's the case here given the timeline of these problems presenting themselves. Any idea for other things I can check before Tuesday?

 

I am no expert but I had a friend who had a similar problem with her speedo and abs. If the speed sensor at the wheel don't work then You will get a fault and with a speed sensor fault the speed was always zero in the car even when on the highway. Wen sensor were replaced car was fine...to me it sounds like a problem with your harness

 

Yea the speedo works off the abs sensors. I think u need 2 working. I have seen it explained in a post somewhere on this board. Maybe search for it? Im sure there us still somthing wrong with your harness.

 

I agree with this

 

I replaced the front wheel sensors with used sensors (both speed and brake wear sensors) from another car, but didn't have much of an effect. Maybe it needs brand new sensors..?

Any idea how I would go about checking for voltage across the harness itself? Just place one probe of a voltmeter into one of the connection points and then ground it at the wheel carrier? Does anyone know how many volys/amps I should be detecting if the harness is functioning appropriately?