clk 230 komp w208 o2 sensor fault

[brutus]

hi there this is my first time using this site. i have a problem with my clk 230 kompressor w208. it keeps flagging the upstream co2 sensor as being faulty. i have replaced the part and had all the codes cleared and within 15 miles the engine warning light has come on again. the car runs perfectly until the light comes on then runs really rich. the light always seems to come on when the engine is at about half temperature. can anybody please help!!!!!

 

[television]

Hello and welcome to the forum, this could be a MAF fault that is upsetting the O2 sensor, unplug it and see how it drives

 

[brutus]

thanks malcolm i will keep you posted.

 

[BlackC55]

It could also be one of the cars with oil in the loom????

Check the wiring too as if this sensor keeps flagging up and the sensor is new I would suspect a wiring fault.

 

[star]

It could also be one of the cars with oil in the loom????

Check the wiring too as if this sensor keeps flagging up and the sensor is new I would suspect a wiring fault.

+1, same thought. oil in wiring

 

[type49]

+1, same thought. oil in wiring

+2

 

[brutus]

i think you guys may be right. i have just cleaned the maf and both throttle boddies and along the way i found that the crankshaft oil seal is leaking! i suspect that the oil is running down the centres of the wires in the loom to the o2 sensor. does this sound about right? how much does it normally cost to do seal and loom?

 

[Uncle Benz]

No, the fault in question occurs at the camshaft adjuster unit, on the front of the cylinder head, and oil tracks down the wiring loom to the ecu. It is ecu contamination that causes the fault to rear its head. Remove the plastic cover at the front of the engine, unplug the connector and look for oil. If you find some, the next place to look is in the 'E-box' which contains the ECUs (rear left hand of engine bay)

 

[brutus]

yes you are right it is the camshaft acctuator at the front of the engine leaking and going all the way to ecu! i have orded new part plus new engine harness £380 for harness!!!!!!!!!!!! ouch. ive still got to fit it yet , not a job im looking forward to. i have managed to open the ecu up with great care and difficulty and no oil has managed to get on the circit bourd. do you think the ecu will be ok?

 

[television]

yes you are right it is the camshaft acctuator at the front of the engine leaking and going all the way to ecu! i have orded new part plus new engine harness £380 for harness!!!!!!!!!!!! ouch. ive still got to fit it yet , not a job im looking forward to. i have managed to open the ecu up with great care and difficulty and no oil has managed to get on the circit bourd. do you think the ecu will be ok?

The ECU is always ok, if it had got oily it could have been washed off

 

[busby20]

yes you are right it is the camshaft acctuator at the front of the engine leaking and going all the way to ecu! i have orded new part plus new engine harness £380 for harness!!!!!!!!!!!! ouch. ive still got to fit it yet , not a job im looking forward to. i have managed to open the ecu up with great care and difficulty and no oil has managed to get on the circit bourd. do you think the ecu will be ok?

I have had this problem on both my SLK's, unfortunately I had to pay for one, but got the other one under dealer warranty. The mod for curing this problem costs about £30, you would think that mercedes would have done a recall on this item and avoided all this cost to owners?

 

[type49]

I have had this problem on both my SLK's, unfortunately I had to pay for one, but got the other one under dealer warranty. The mod for curing this problem costs about £30, you would think that mercedes would have done a recall on this item and avoided all this cost to owners?

I believe the part is £14 & could have saved a lot of money for people if fitted as a recall. As Malc said, the ECU can be cleaned out. Often the lamba sensor is also full of oil. You will also need a new cam magnet (not adjuster)+ little bung + engine sealant or else your new loom will suffer the same fate:-( As to fitting the loom, it is OK if you have a ramp but........
part of the loom goes under the inlet manifold at the back of the head & is quite fiddly:evil:

 

[brutus]

thanks mate thats a relief. when parts are fitted i will let you all know the outcome.

 

[RossiRoss]

Me too!

I have had the same problem with the Sensor on the front of the engine, which was replaces and the end of the loom cleaned with brake cleaner, and this now appears free of oil. Check engine light cleared and ran well for the next 2000 miles.

Dam light back on today and power loss as before.

Have been suggested may be oil in o2 sensor, however I have no idea where this is. I have checked all the connections I can see and get to under the bonnet.

Is there any alternative other than a new loom at c.£400 + Vat and 3hrs labour????

I love my CLK 230 w208 - any advice anyone could give would be most welcome and if it can be solved without a new engine loom you will join my Christmas card and lottery winning list (ie people I will look after when I do eventually win the Lottery/euro Jackpot!!)

Andrew