AtlanteanTitan

Hello everyone, I own a 2001 CL600 with 120K on the odometer. Got an error code indicating cylinders 10, 11 and 12 misfiring and a code for cat converter. Had both the coil pack and the ignition module rebuilt and the injectors were cleaned and tested but the problem still exists. The company that rebuilt both said that I can send them back and if needed they will repair them although he does not think that neither the coil pack or the EM is bad because he tests them before sending them out, and he was very nice and helpful taking his time with the mechanic going through the scanner. We let him know that after clearing the engine light, it seems that engine light goes on after putting the car in gear. He thinks it might very well be the cat converter because of back pressure for those cylinders (10, 11, 12) since the three cylinders belong together in a group of 4, each including 3 cylinders. I would like to know if anyone else had the same issue that might be able to help me diagnose, and could it be the before and after cat sensors as well or maybe something else. Thank you all for your help.

ItalianJoe1

I believe the early v12 has 4 split exhaust manifolds, meaning there is a front and rear on each side, each with it's own cat. Cat codes and misfires on 3 common cylinders, could very well be a clogged cat. Pull the manifold and see how it looks, if there's any loose material just replace the cat.

knowbenz

This, that engine has four front cats, 1 for 3 cylinders