I have an aftermarket air shock on the back right. It is a replacement for the last one that failed and leaked oil out of the top into the electrical connector.
Now after a few months the car is showing CATS fault again. I checked and yep, there's oil in the top of the strut again. I cleaned it all out and blew it out with IPA, I connected it back up and yay no CATS error, until i started reversing down the path then here it is again arghhh. The icarsoft says cats short to gnd, but if you turn off the car and back on it goes away until you move. If i disconnect rear right, it shows both errors; rear right damper disconnected and cats short to gnd. Any ideas where the short can be? (most obvious place to start?)
Is the CATS module under the passenger seat in a 2008 vanden plas?

the hunt continues.......

 

If your rear Air Spring and Damper is aftermarket it will not support CATS; I cannot imagine CATS working all that effectively if one or more of ones Dampers are aftermarket? Accordingly, you could consider bypassing the CATS System Faults by fitting the following resistor to the loom connector at the faulty one?

20pcs Metal Film Resistor 1W 1% 1K ohm 1Kohm 1KΩ | eBay

I simply pushed each end of the resistor into the female sockets in the connector and then heat-shrunk it to secure?

Did this to all four and have never seen a CATS System Fault message again!