Rogerthat1

Hello Guys. I recently purchased a 2004 Audi A4 B6 1.8T . The car is not in a prestine condition but I hope to get her there soon. The previous owner did not pay too much attention to the vehicle and I am hoping to sort out all the minor odds and ends to have this vehicle in a perfect condition. So far I have had my turbo rebuilt , replaced PCV and PRV, N75 valve ,oil and spark plug change. However I noticed that the car was using alot of gas and I had some gas fumes coming from the exhaust. Recently the car overfueled and did not want to start. I checked the spark plugs and they seemed to be wet with fuel. At first thought it might be injectors that are stuck open but they are fine. I did a fuel pressure test and they seem to hold pressure well with no injectors leaking. I then had the car scanned with a VAG and the got the following codes:

- Manifold pressure/ Boost sensor ( G31 ) P0238 - 001 - Signal too high
- Manifold Barometric pressure sensor ( G71) (F96 ) P0106 - Implausible signal

I then realized it could be the MAP sensor wiring that seemed dodgy to me in the first place. That is the sensor that mounts on the SMIC (intercooler). The wires have been cut before the harness that plugs into the sensor but the wires colors do not match where they are joined ( seemed like the previous owner did some strange wiring himself) . I have done some research online and most people say that the voltage at the wires should be with ignition turned on :

5V ( power wire from ECM)
1-5V ( signal return)
0 V ( ground wire)

The most common MAP sensors have a 3 pin but this model Audi has a 4 pin.I have no idea what the 4th wire is supposed to do. I then got my multimeter and the voltage readings are completely different from what most people say the voltages should be. My voltage readings and 2 tone wires connections are as follows:

1) Brown/Black - connects to Brown/Yellow = 0.25V
2)Blue /White- connects to Blue/Brown = 12.23V
3)Purple/ black - connects to yellow/grey = 0.02V
4)Green/Black - connects to Grey/Red =0.50V

My concern is that the power wire seems to be the 12V wire. Is this normal for this car? Should it be 12V and not 5V? I would also like to know which one of these wires is my signal wire? The car feels like it is in limp mode because of this. I really need some help with these wires. I would hate to purchase a new sensor and have the new one blown because of incorrect wiring. Any advice would be appreciated. Or if someone with the same car can test the voltages at their sensor and report back too me would make my life so much easier. Thanks in advance

Rogerthat1

Anyone? I forgot to add that it is the BEX 140kw version

lyleswk

I have found this document useful twice in my troubleshooting of headlights and FCM. I had convinced my self at one point that is was for a B5, but can't find that reference...

http://www.vaglinks.com/Docs/Audi/B5...ingDiagram.pdf

Rogerthat1

Thank you for the response. Most people have the 3 wire map sensor> 5v power , signal and ground but mine has 4 wires. I thought the reason might be because it is a BEX. The voltages are also completely different than the 3 wire map sensors. I thought the 4th wire might be the temperature kinda like a MAT sensor instead of MAP. I am so confused. I hope to get someone with a BEX willing to do the favor of measuring the voltages at their MAP sensor so that I can have an idea how to wire it properly.

lyleswk

Well did a little searching and didn't realize the BEX was that different than the AMB. Most of the folks on here have the AMB. It sounds closer to the Audi TT 225 engine and must have something to do with the second intercooler. Unfortunately, I haven't had to work on my son's TT, so I will be less help than my no help normal

Rogerthat1

Thank you for taking the time to do some research on the topic. I have been searching all over but cannot seem to get the information, not to mention a wiring diagram of the sensor. I will dig in a bit further into the Audi TT 225 wiring. I might get lucky on getting a wiring diagram of this engine. The other option I was thinking is I am going to remove the sensor and get the part number and do some searching on the part number and hopefully get some information.