Check engine light issues - 2000 New Beetle

My check engine light came on in my 2000 New Beetle last weekend. I was driving on the interstate when the light came on. Since I didn't notice anything immediately wrong with the car, I decided to push on for a while. When I stopped for a bathroom break, I decided I should go to AutoZone for their free check engine light diagnosis.

My car is returning the code P1557. Here's the information I got from AutoZone on the code:
Definition: Charge pressure positive deviation
Explanation: External leak on intake or exhaust side
Probable cause 1: Failed charge Air pressure sensor
Probable cause 2: Failed wastegate regulator valve
Probable cause 3: Failed turbocharger

Since getting to my destination was critical and all the driving would be on the interstate, I decided to push on and try to avoid pressuring my turbo system. The car successfully completed the drive.

The other night I had to drive down the street to get some groceries. On the way there, the light came on after diagnostics completed (as expected). On the way back, however, the light came on and then went back off. Is this normal? I feel that this might be more indicative of a loose hose or valve (the wastegate regulator?) since it sometimes passed diagnostic checks.

Thanks in advance,
Winter Phoenix

The actuator is probably bad, or the vanes are jamming.

Check the actuator with a vacuum pump. It's supposed to hit the stop at 18 inHg and back off at 17 inHg.

Sometimes the N75 regulator valve quits but as far as I know it would fail safe (fail to supply vacuum - low boost).

Has the intake manifold and EGR valve ever been cleaned on this car?

jcrews said:

The actuator is probably bad, or the vanes are jamming.

Check the actuator with a vacuum pump. It's supposed to hit the stop at 18 inHg and back off at 17 inHg.

Sometimes the N75 regulator valve quits but as far as I know it would fail safe (fail to supply vacuum - low boost).

Click to expand...

When it comes to car knowledge, I pretty much know how to drive them, fill their fuel tank, and change a tire. I appreciate your help, but most of what you said was pretty far over my head. Where is the actuator? When you say vacuum pump, I assume it isn't the same as a vacuum cleaner :-/.

Thanks again for the help
WinterPhoenix

frugality said:

Has the intake manifold and EGR valve ever been cleaned on this car?

Click to expand...

I don't have the service history from before I bought it, but I don't believe I have ever had it done. The car's approaching 95k miles, is this something that would have been done during other trips to the shop?

Intake cleaning isn't a normal service requirement. You should check it though, because some get clogged up with soot badly. With ULSD and EGR, I didn't have much of a buildup at 140000 miles even after all the years with regular 500ppm LSD.

Get the tool for spring clamps with the remote cable. Most tool shops carry them, including Sears.

To check the actuator, go to autozone and ask to borrow the handheld vacuum pump. Hook it up to the N75 vacuum port (2nd from the top on the gray capped valve). Start pumping and you should see the vane arm begin to move with a few inHg. At 18, the arm should stop. Release the vacuum slowly and watch for hanging. You can also push on the arm with your thumb and feel for binding. Travel is about 3/4".

For more information, look for "how to diagnose and troubleshoot limp-mode"

jcrews said:

For more information, look for "how to diagnose and troubleshoot limp-mode"

Click to expand...

I got that one bookmarked:
http://forums.tdiclub.com/showthread.php?t=179589

Wow, thanks everybody. I'll have to check into this when I have a break from classes, hopefully this weekend. Roughly how likely is it that I'm putting my car at risk by driving it around on errands?