P0138 code detected

[johnny679]

Hi all , im getting a P0138 read from a scanner , which i believe is a o2 oxygen sensor?? , under the car ive found two sensors before and after the cat , the one after looks as though its never been changed as its more difficult to remove , the car in question is 2002 C180 , with a 2.0 petrol and autobox.

 

[Larkone]

It should have said Bank 1 Sensor 2 for that code which would be the rear sensor.

 

[Stocious]

Or pre or post

 

[Stocious]

Do Mercedes use the post cat o2 as an indicator of cat efficiency same as other manufacturers?

 

[johnny679]

the rear o2 sensor removal looks a right sod ,especially the wiring going up behind the metal heatproof ,is it clipped above this and are both sensor leads identicle as it is further back behind the cat , any tips