UA: 2004 allroad c5 4.2 question
 

just bought this allroad with 4.2 bas engine, with lots of problems. it runs normal, drives good, but sometimes it gets very dull. rpm does not increase more than 1800-2000, looks like it decreases power for some reason. is there any wiring schematics and locations manual available? i read a car with vcds and it shows some errors on oxygen sensor, knock sensor, i would like to check them and wiring to them too

If VCDS calls out an oxygen sensor, the first thing I would it to replace it. It not expensive and fairly simple to replace. As compared to most other stuff on these cars.

Then clear you alarms take a long drive and check for new error codes. Google the codes, or post them here, if you have problems understanding it.

A Bentley service manual is also a good investment.

yes, i tried this, erased all errors but some appear again. P0327 and P1128. what could it be?

From Ross-tech:
17536/P1128/004392 - Ross-Tech Wiki

and

16711/P0327 - Ross-Tech Wiki

For the knock sensor, if wiring looks good, replace the sensor.