Hello- I'm about to embark on a road trip and just noticed the warning light for the subject interlock is on (red).
Any suggestions/advice?
Thank you

 

Did you engage it by mistake?

If you go up to 30mph does it go out?

Is pedal brake feel affected?

Fluid levels ok?

 

This happened to me last week. Check the connections of your wheel sensors. They are barrel shaped and have brake pad wear sensor and wheel sensor connections. My problem was a loose brown ground wire connected to the trailing arm from the barrel. If you are not usuing the rear undertray, it seems likely that your problem is related to the rear wheels. If your ecu does not get a signal from a wheel sensor it cannot provide ABS or All wheel drive functions. Did yours "beep" also?, mine did and it was kind of scary?
Steve

 

Any one have anymore to add on this.... My C4 is doing the same thing..

The warning light for the Diff lock will come on from time to time. Mostly on long trips, but it re-sets as soon as I turn off the car...

Any help would be great.

 

20 year old Ground wires............

 

Mine was cured by replacing the ignition coils. Apparently the system is really sensitive to electrical noise. It's been over a year and haven't had the PDAS lights come on once...(except at startup of course)