Poli84

So you had the same problem as I described (problem 3), and installed 2 new solid state accelerometers and problem is now gone?
No more 4WD light when travelling at speed?

And was this the lateral or axial acceleration sensor?

GeorgeK

Yes, same symptoms, after 15 minutes on the highway. One accelerometer was bad. Swapped it for a factory one from a wreck, solved the issue. Then bought 2 solid state units. No problem in the last 2 years.

Can not remember for sure, think it was the lateral one. KTS found it.

Poli84

Good man, thank you very much.
I could take the punt and just purchase one but perhaps it's worth while to just change both out at the same time.

964surfer

Any updates on this? Also, I cannot seem to find information on the location of either sensor if someone would be so kind as to describe where to look. Thank you!

John McM

Panel on the transmission tunnel close to the gear stick

Poli84

Replacing my sensors have been "adding to the list" so not something I will be doing short term.
Once I do so however, I will report back with hopefully positive results.

964surfer

Thanks! Accessed from inside the cabin then? Or underneath the car?

John McM

Inside the cabin. On the right hand side of the tunnel.

964surfer

Thank you Sir!

964surfer

Quick update: it occured to me that I could simply remove the sensor and swap another in off my friend's 964 without risking a $400 purchase that may or may noy solve the problem. I did and...no warning lights! That being said I reinstalled the original sensor and the lights still have not come back on. I am thinking this is only temporary but at least I was able to isolate the issue down to that unit. Will order up the solid state version if it happens again.

biggynuts01

I just developed the exact same problem as the OP. Its different than most problems that I have searched.

No warning lights at start up or initial drive. Its when I drive ~15 min at freeway (60-80pmh) speeds that the PDAS light comes on and alarm comes on.

If i drive on the streets (30-50 mph) and go from stop light to stop light, the car does not have any issues.

It seems that the PDAS light comes on when the car is driven at freeway speeds and the speed must be consistent.

It makes me think its the speed sensor on the transmission - i have a 89 C4.

What do you guys think?

-nick

Does anyone find that there warning lights coincide with hitting bumps/potholes? After driving in the rain, on the highway, hit a bump, about 25% of the time my pdas warning will chime too. Still haven't tracked this one down. The code clears on restart and I haven't had my scantool handy to get a read after it happens. Cleaning the accelerometers is on my to-do list.

NateSaJack

I had this last year, started when I hit a pot hole and after a few weeks occurred everytime I drove. It was a broken wire between the abs sensor and vehicle loom. At the same time a fellow RLer was tracking down a broken wire under the seat.

It was intermittent until it broke completely. Found it by buzzing out the relevant connections in the abs connector. That showed it to be rear pas side. Worked methodically, first the car loom, then the bridging piece (where the movement is so could have started there I guess) and finally abs sensor itself.

biggynuts01

Which sensor are you referring to? The abs pressure sensor in the frunk or the speed sensor?

NateSaJack

It's all on here here

I started with the big abs connector in the frunk. Looked for resistance to each of the abs wheel sensors. Had none at the rear left.

I disconnected the plugs that go into the biege cylinders and bridged them so I could check for a complete circuit.

This only worked once the wire had failed completly.