Killahkal88

So last week the CEL light came on indicating that my pre-cat o2 sensors needs to be replaced.

Specifically P0141 (sensor heater circuit malfunction) and P0136 (o2 sensor bank 1 sensor 2). I assumed both goes hand in hand.

I bought 2 brand new Bosch PnP (plug n play) oxygen pre-cat sensors and installed them last week Friday. The CEL disappeared, but the same codes came up yet again...

I double checked the wiring harness for the sensor wires and have found no abnormalities. I doubt there's any issues with my cats as 2 months ago the smog tests proved that it passed with flying colors.

I am aware that the P0410 code is the air injection, but I'm just going to ignore it for now as it probably involves the smog/air pump. My concern is mainly with the o2 sensor codes.

Anyone have any solutions or suggestions on how to go about in fixing this? Greatly appreciate it!

Killahkal88

Is it possible that the MAF sensor could cause these codes to pop up?

leapyfish

The last link in my signature is a download for a service manual for the Chrysler Crossfire, its the same engine and systems as your slk 320. The code listings and troubleshooting guides are all there.

Killahkal88

Yeah fml. I just realized that it's the post cat sensors that needed to be changed and not the pre-cats...Oh well I suppose they are due soon anyway. Good looking out!

Cigar Pete

For all SLK 230 owners out there, my mechanic shared something with me recently that I think is really good information.
I had a CEL light on and the Pre Cat O2 sensor showed as failed.
Before he did anything he popped the cover at the front of the supercharger and checked the connector on the Cam sensor, then he checked the connector on the O2 sensor.
Apparently the cam sensor can leak oil and it migrates through the sensor, down the wiring harness and can contaminate the O2 sensor connections,
If that is the case a simple cleaning of the oil from the connectors is called for and the cam sensor may eventually need replacing.