My 2010 Cooper S quit on the highway and had a significant misfire when I tried to re-start it. I had it towed home and checked the fault codes SES was on also. There are 8 code instances primarily referencing multiple cylinder misfires and calls out cylinder 2 on 3 instances. I also get a P0055 code that states O2S heater resistance bank 1 sensor 3. This has confused me because I can only find 2 O2 sensors. One on the down pipe and one behind the catalyst. Does anyone know which sensor this relates to? One more question, one of the codes listed was C342D, I can find no reference of this anywhere. Does anyone know what it is?

 

I couldn't find anything specific to C342D other than the C stands for chassis, and the 4 stands for emissions.

 

Hello, celticfc. Did you resolve the issue? I have 2010 Cooper Justa and yesterday I got the same codes as yours - multiple cylinder misfires and P0055 and C342D.

TIA

jh

 

Final diagnosis was burnt out valves on # 2 and 4 cylinders. Pretty much fried the motor. I ended up buying a used motor rather than trying to rebuild it. That P0055 I think is only diagnosable through the BMW service tester. I would suggest you do a compression check as a starting point.

Good luck

 

Thanks, celticfc. That is what I was afraid to hear. I'm not good with the cars and I might need to take it into the indi shop for diagnostics. Do you know what would have caused that failure? what i have done before I noticed something was to put the Chvron system cleaner. I have done so many times in the past and I noticed the decreased MPG and power, so I got some from Amazon and put it in about 2 weeks ago. My wife told me something is not right with the car after putting it in - engine is louder than before, according to her. And last friday after work when i hit the accelerator to merge into freeway, the car shook and misfires. I got home somehow, but the car is still rough at idle with all the codes.

But thanks for the quick response.

jh