2001 Volkswagen Passat water on back seat driver's side

I would tape some news paper up over the sun roof on the inside of the car then put water on the roof and see where the water marks are, just an idea!

https://www.youtube.com/watch?v=Hbr77jfWwOk

Sunroof drains are a common problem on many models. Cleaning or modifying the sunroof drains usually takes care of the problem. You may resolve your problem. I believe that the trouble codes are unrelated and may need professional diagnosis as you need VAGCOM to adapt the throttle.

1) Check the pollen filter, its probably in a poor state if its not been changed yet.
2) Check the bulk head drains.
3) Check the sun roof drain pipes (usually run from under the sun roof, down the door pillars to the wheel arches, often covered by an plastic inner wing) clear out all the mud and debris.

1) Could be your sun roof drain, if you have a sun roof. The drain runs from the corners of the sun roof recess usually down the front side pillars and our of the whell arch. Check the flow path is clear. Had to clear mine a couple of weeks ago, found that mud was piling up under wheel arch behind the plastic arch screen, had to dig it out, ok now.

2) Could be your pollen filter is blocked, check and change.

3) Make sure all your door seals are good.

4) Make sure all the engine bay, bulk head drainage channels are clear.

5) Check your coolant levels, if the heater matrix has a hole, could leak inside the car, can be fixed with a proprietry solution, one I know is Radweld., pour it in the header tank, top up the coolant and go for a spin.

the spacer bar holding the passanger seat in place is cracked/rusting? If so you will need to get the section cut out and a new plate fabricated to fit and welded in. Check the door seals are intact as well, the water might be coming in there down to the lowest point.

all sunroofs have drain pipes, usualy 4, one on each corner, they usualy run down the A pillars at the front and poke out near the kick panals by the footwell. the rears often run down the C pillar to the vicinity of the boot.
open the sunroof up and carefully pour lots of water around the drain gulley of the sunroof, you should see it pissing out onto the floor at the front and rear on each side. make sure water goes down all 4 corners of the sunroof and check. Pipes can come of at the roof. also the drain grommets block up.

common problem on passats also is the pollen filter housing letting in water (under the scuttle panel beneath the bonnet. on left hand drives though, this fills the passenger side only (left). not sure on RHD which side pollen filter housing is on , but when they leak the water fills up inside the car on one side only, which can flow front or rear depending on car being parked up or down hill.
the seal between the pollen filter housing and the bulkhead often leak, if you press down on the plastic housing you may hear the seal squelching water. there was a recall on this, so it may have been done.
If the comparment under the panel (where the battery is) is filling with water, there is a drain grommet under the batter that also blocks up sometimes, causing it to fill up and flow in where it shouldnt.

Under the boot. or hood near the windshield thanks Ollie www.germancardepot.com

I don't think it has anything to do with the sunroof. I think you have a leak either around the windshield or under the cowl where the wipers are attached. If it's in the cowl area probably over the blower motor housing on the right and the water is following the vent system to the drivers side. Please let me know how you made out.

Thank you

Under the Drivers carpet right in front of the Driver seat.
There is a black box the controls your electronics.

The carpet need to be pulled back from the firewall (where your feet go) Under the pedals. You need to remove quite a bit of interior trim to get to it..

Then you need to get dry every thing out. I'd disconnect the battery while doing this.....

Could be a bit of trouble.

That sounds like you problem.

Hope this helps...

I had exactly the same problem about three years a go on a 96 passat (just before the model change).

It turned out to be the grommet where the bonnet release cable goes through the bulkhead had pulled out. I pushed it back in and plastered a silicone sealer over it and it has been fine since.

However, a couple of months ago, I noticed that the inside of the car was very damp again. The carpets and foamy stuff have all been taken out. This time, it was just the drivers footwell that was sopping wet. The grommet around the bonnet release cable is still in place. I've dried it all out and we've had a couple of torrential rainstorms since then, but no water has come into the car so I'm stumped.