HSB

Hi,
I am still trying to iron out my electrical gremlins. My traction control light comes on usually at 60 mph or above while traveling in a straight line. Adrian suggested that cleaning the center tunnel accelerometer might remedy this intermittent problem. Anybody have any experience in doing this. I would appreciate any help before I have to take it in to Hans. Thanks in advance. Harpreet (90 C4 Cab).

Adrian

Dear Harpreet,
When the weather clears I have to do the same thing. I have not donethis personally (cleaning out that is) but I am informed by fellow 964 owners that it does work. Removing the accelerometers themselves is very easy. I have had them out. What I have not done is removed the lid of the accelerometer before. The tip is only do one at a time. Do not remove them both together. If you mix them up you have problems.
Ciao,
Adrian
964C4

HSB

Adrian,
Thanks for the prompt reply. I was wondering where they were located, how to best remove them-- under the car or is there an access port through the tunnel. Any procedural advice would be greatly appreciated. Thankyou, Harpreet

DaveK

On most cars (at least, on UK ones) there is a panel in the side of the centre tunnel held on by 2 screws. Take this off - and the accelerometers are behind it.

Adrian

Dear Harp,
Dave has told you where they are, in the centre tunnel with access from the right side. There is no procedure to remove them, you will see the connector, remove it and remove the screws and take it out. Treat with some care.
Ciao,
Adrian
964C4

HSB

Thankyou Dave, Adrian for your help.

Harpreet

HSB

I took the car in to have other codes cleared(repairs done) so that I could pass state inspection and the mechanic scanned the PDAS code and this time it showed that it was related to the transverse locks. The mechanic suggested flushing out the system. He thinks that the "pin" is slow to engage. Anybody else experience this situation. Thanks

Adrian

Dear HSB,
This is possibly telling you that the tranverse (lateral) differential lock slave cylinder is worn out or the pack is worn out. The later is very expensive to fix. Depending upon your 964 model year you can try adjusting the pack.
A system flush and bleed may help.
However the fact that your problem is intermittant I would still be looking at the transverse accelerometer first. It is the easiest and the cheapest and based on your symptoms the most likely villain.
The PDAS control unit is dumb. It knows something is not engaging in time but it does not really know why. The transverse lock is partially controlled by the transverse accelerometer. It pegs out at 60 mph and I suspect yours is going open circuit at 60 mph indicating the voltage pick offs are dirty.
Start cheap and work towards expensive. The very first fault I ever had with my C4 ended up being one of the lock slave cylinders. In my case the longitudinal one.
Ciao,
Adrian
964C4

HSB

Thanks Adrian I will do this first. It is interesting that the computer showed that the fault was set at 61 mph.
Harpreet

Adrian

Dear Harpreet,
That says as I said in the begiining, lateral accelerometer pegging out. This should be checked first before going underneath.
Ciao,
Adrian
964C4

Carl Muckenhirn

Adrian,

I've developed an intermittent PDAS warning. Intermittently, upon application of the brakes the PDAS and Brake warning lights will illuminate, for approx 20 sec. and then go out. Intermittent is approx 1-2 in an hour of driving.

I've checked the accelerometers (swapped them from an other vehicle) and the situation still occurs.

I'm just at 98K miles. Would the diff locking system, or ABS be your first point of investigation?

thanks in advance,

carl.

'89 C4

Adrian

Just a followup. I have a similar problem to Harpreet. The waether cleared enough for me today and go and get my hands dirty. I can now confirm my transverse lock, slave cylinder has failed. My rear diff lock will not engage at all when commanded. The centre lock is engaging.
So Harpreet in my case it was not the accelerometer but the lock engage mechanism itself.
50/50 chance for you.
What I recommend you do is engage the traction control program and drive off. If you hear the system clanging and grinding its way through life and you can feel the massive understeer you locks are engaged and fully functional suggesting an accelerometer problem. However if you cannot hear the bumping and grinding and the fail warn comes on before the system disengages at 40 kph then it points to a lock failure and in your case as well the transverse lock.
Ciao,
Adrian
964C4

HSB

Sorry to hear about your cylinder failure. I am going to get my new jacking plate welded tomorrow and then I will try testing the car. My car has 58,000 miles on it and has been well maitained: however it has driven more miles on the back of an auto transport in the past 12 months than with all four wheels on the ground( sold from one dealer to another after the original owner Passed away). I did try to engage the traction program last week and it did make the above mentioned noises and then disengaged .
Last question, How difficult is it to change the slave cylinder as in your car?

Adrian

Nothing to be sorry about things break. Changing the slave cylinder is easy having to use a Bosch Hammer for the system bleed is the annoying part. You also have to check the torque and adjustment (if you have the adjustable type installed) of the actual lock itself. If that has failed and you cannot adjust it (move the plates together) then it gets expensive. This rarely happens but my 964 has been a daily driver all its life and the traction control kicks in often around this area so I might be looking at worn out diff locks as well. It was going to happen eventually.
Ciao,
Adrian
964C4

HSB

Hi
I got my jacking plate welded and then went for a spin. The traction program engaged properly several tmes and then disengaged at proper speed. I guess on to accelerometer cleaning this weekend.