Question about 1999 Volkswagen Cabrio
I am getting a P0171 system too lean on bank one, it seems to idle rough and it shifts rough. I have had the code cleared only to have it come right back on. Help ~ Kimberley
I am not familiar with Cabrios. I am very familiar with VW Passats and Audis (VWs in disquise) . Please read my experience with my 1997 VW Passat VR6. Since your Cabrio is a VW, it may have a very similar problem.
I had a similar problem to yours with my '97 Passat. Bank One Failed was the code I observed. To fix it, I removed the throttle body from the engine by disconnecting the air intake, two small diameter water hoses and one or two electrical plugs.
The throttle body (sounds complicated but it isn't at all) was dirty. I removed the four Torx machine screws which attach the throttle body to the engine and put the throttle body in my wife's largest stainless steel mixing bowl. I bought a large spray can of "Throttle Body Cleaner" and a cheap toothbrush. Next I spent about an hour scrubbing a thin layer of carbon deposits from the throttle body. I had to use my thumb to hold the throttle door (not a technical term :-) open and sprayed/scrubbed/sprayed/scrubbed until everything, even the very edge of the little metal throttle door, was all shiny and clean. When I was all finished with cleaning the throttle, curiosity got the best of me. I fearfully removed the cover from the electronic throttle control mechanism to see what it looked like inside. After taking a long look at it's inner workings, I carefully and reverently replaced the cover and prayed to God I hadn't disturbed anything by breathing on it. That gizmo is REALLY complicated! Some piece of German engineering.
I replaced the throttle body on the engine. I reconnected everything as it had been before. Total time less than three hours.
Next, used a trick known to sage VW Gurus around the world.
You see, whenever you
1. Replace your VW battery
2. Mess with your throttle body
...you MUST perform a "THROTTLE ADAPTION PROCEDURE"
This sounds (and is) tricky and complicated. I didn't want to do a throttle adaption procedure because I was sure I would mess it up.
I got really lucky and found a friend of a friend who is an experienced VW mechanic. He let me in on a little secret.
John said "Buddy...
==>disconnect the VW battery for forty-two minutes."
"When you reconnect the battery, the computer chip will return your throttle settings to factory presets."
Woo Hoo! I disconnected the Passat's battery. I set the timer on my oven for forty-two minutes. When the oven timer went off, I reconnected the battery. I connected my laptop's serial port to the OBD computer port in the Passat's passenger compartment and used my Ross-Tech VCDS software to clear all of the OBD codes. Then I performed another scan. The Bank One Fail code did not re-appear!
My Passat has idled smoothly ever since!
Kimberly, I know it is hard to believe that a thin layer of carbon deposits would have such a profound effect a VW engine's idle. Apparently, this is the case. The throttle door was being held slightly open by the accumulated carbon deposits. The throttle position is so very sensitive that it caused the engine to log
the BANK ONE FAIL code.
I hope this helps you. By the way, I went to Sears hardware department and purchased the Torx socket required to remove the throttle body.
Posted on May 16, 2009
What tha generally means is your o2 sensor is throwing a fault code. this is mostliely due to the fact that your TPS (throttle postion sensor) is not functioning properly. this is why there is also a rough idle to the vehicle. have the TPS replaced and the problem will be solved.
Posted on Nov 12, 2008
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