My 03 225 TT ran into some problems during my return trip from SF to Santa Barbara this weekend. It was raining heavily the entire time so I'm wondering if that could have anything to do with the issues (its the only thing out of the ordinary I can think of...)

The car seemed to hesitate under anything but modest acceleration at low and high speeds on my way back. I'd start accelerating and the engine power would just drop off completely until I took it easier. Then I could maintain whatever speed without issue. When I pulled over at a rest stop the car wouldn't restart. It would crank, turn over, but then die immediately.

After waiting 40 mins for a tow truck the car somehow was able to start and I made it home under the same issues. I tried starting the car again at home and it just cranks without turning over now.

I ran my cheapo ebay scanner and pulled these codes:

VCDS-Lite Version: Release 1.1
Component and/or Version: 1.8L R4/5VT G 0003

2 Faults Found:

16519 - Oxygen (Lambda) Sensor B1 S1; Heating Circuit: Malfunction
P0135 - 35-10 - - - Intermittent

16705 - Shareware Version. To Decode all DTCs
P0321 - 35-10 - Please Register/Activate - Intermittent

I've found that 16705 is an engine speed sensor and 16519 is an 02 sensor. Are these two parts failing related or is one causing the other? Is this just a simple job to swap in replacements? Any chance water damage/rain caused this?

 

The O2 sensors are under the car... I would check the junction under the little cap, rear of engine, pass side framerail. Theres two connectors, take them apart and use dielectric compound on them and reattach. Bad design...

 

Well I finally got the parts in and replaced the O2 sensor easily. It was a pre-cat sensor so it was accessible under the hood all the way at the back of the engine near the exhaust manifold.

The G28 engine speed sensor has been giving me hell. I unhooked the connector easily enough, but the actual sensor is crammed under the car inbetween the oil filter in a really tight spot. I can see the sensor, but not the actual fastener holding it in place. I spent at least 2 hours screwing around with it and got nowhere. I can barely get a tool in there.

Has anyone removed it (using a jack/jackstands) got any tips? Is there a special tool that helped? Even knowing the the size socket size would help a lot (im not sure which I need because I can't actually see it).

Note: for future reference the G28 sensor can be removed with a 5mm hex using a 1/4 ratchet+extension. Oil filter needs to be removed first.

 

So I finally got the G28 speed sensor replaced in addition to the O2 sensor but my car still wont start. It wasn't easy getting that speed sensor out, so I'm a little bummed that it may have been for nothing. The battery was uplugged the whole time I was working on the car (that should clear the old codes, right?) and when I ran the scanner again the exact same ones came up + a new one: 18010.

Can you guys please make some suggestions on what else I could try? I really don't want to have to tow the car to the dealership just yet.

 

Just used VCDS-lite again and cleared the codes. No codes came back with the module scan or the auto-scan (tried multiple times, is there any other way to be sure?)

Car still cranks but the engine won't fire up. What could be causing this but not throwing a code? Could the engine be flooded? Clogged fuel filter? I'm really not sure what to check next.

 

This is the common problem most of us face. Even i had experienced this many times. Thanks for sharing. I found your suggestions useful.