Correct me if I am wrong. Only CA emission vehicles have LDP's. That nipple is vacuum for the LDP. If your '99 Grand Cherokee is a Federal Emissions one that would just be capped off.

Just to add further confusion, I thought ALL 01 XJ's and CA 00-01 XJ's had the LDP...

I think if it were me I'd try capping it off if I couldn't find the hose, clear the code and see if it comes back or not.

That is my understanding too. '00's XJ's can be either. All '01 XJ's are CA emissions.

Now he says he has a '99 Grand Cherokee. I want to say a '99 GC is a coil bar engine. No distributor. Also want to say that '99 GC's have the 0331 head. Despite a '99 XJ not having that head. Also want to say that a '99 GC can be either Federal or CA emissions.
Not sure of any of that. LOL
But if his '99 is a Federal Emissions one then it would explain why he can't find the hose. But dave1123 makes it sound like it is pretty hidden in an Grand Cherokee. Unlike a XJ where it is right there.
Wonder what his white sticker on the firewall says?

I

Hey folks, Does anyone know the size of the vacuum line that goes from the LDP to the intake?