ML320, O2 Sensor Replacement, Engine Code



I have a Mercedes ML 320, 2000.


I just replaced all four oxygen sensors but the "Check Engine" has returned right after the replacement. 


The codes that have been indicated: 157, 161, 135, 155, 141 and 134.


Do you know why those codes would appear even with all brand new Bosch oxygen sensors? 


I am so puzzled...