Tomfun

During an attempt to diagnose a strange set of warning lights (turned out to be slightly low brake fluid), I became curious about my PDAS system. Here is the scenario:
- Driving around I occasionally see the light flash when I go over a pot hole or similar.
- Pump runs at startup as it should, presumable until it reaches suitable pressure and then shuts off.
- No warning lights while driving around.
- No faults found when querying with the Hammer

However, with the hammer hooked up and attempting to use the "drive links" section, I get behavior that I don't believe is typical:



When Transverse lock is selected, I don't hear anything initially. Each subsequent push of "1" results in an audible pulse from what I assume is the solenoid in the frunk, but I can't really say that I hear any activity from the back/transmission area.



When Longitudinal lock is selected, I immediately hear 10-15 rapid pulses from the front trunk, but no change in the counter on the screen. Subsequent pushes of "1" create an additional pulse which is registered on the counter. Still no sounds from the back of the car.



I then started the car and engaged PDAS via the console switch (light blinks as I believe it should), however driving around and turning in tight circles is no different than normal, which indicates to me that the locks are not, in fact, engaged.

So the question is, is the behavior I experience with the hammer typical/correct, and I just have seized diff locks? Or is something else going on?

Thanks in advance.

Tom

Tomfun

Selfish bump. Is someone with a C4 able to comment on the behavior with the hammer?

Tom

Spokes

I haven’t investigated the clicks and clunks when using my PDT999 to flush the fluid, but it all works with fluid pumped out in pulses. Anyways, to you other question, if I engage the 4WD system via the console, I am definitely in a lock diff situation. Limited driving circle and wheels are all engaged, very similar to my jeep when I am in 4wd low. At about 15km the PDAS disengages.

JamesObear

Tom, you could try the same Hammer test on my C4 to compare if you like?

newsboy

Get the same light occasionally going over a bump. Do not think it is a problem.1990 C-4

Tomfun

Thanks James, I'll take you up on that next time I head to Vancouver, hopefully in the next couple weeks.

Yes, I know that isn't a problem, I meant it as a data point that the computer is working as you would expect and theoretically trying to actuate the locks.

Tom