Maintenance Advice

Got a service engine soon light on a 2002 525. Checked the codes and cant remember precisely, but think they came up (best I remember)

19 - Ignition Coil on Cyl 1
C6 - Oxygen sensor at operational control limit Cyl 1-3
C7 - Cat Coverter inefficient or something like that

I reset and it came back sooo... must address
I have had the car for about a year and 20,000 miles and it is at 67,000 total.

I checked codes before and have seen it complain about the 19 error before when changing oil. reset but comes back. Been meaning to change the plugs as I doubt they have ever been changed.

Car is still performing fine gets consistently over 32 mpg on highway.

So I will go ahead and change plugs. Should I change the coil on cyl 1 at the same time or could it just be the plug? I could change the plugs reset and see if the errors come back. But hate to dig in twice, and hate to waste $$s.

Do you think I need an O-sensor? Just looking for order I should approach this. Any thoughts? Thanks any response.

you may need the coil you will have to check it but the other codes sound like they are related to the cylinder 1 coil code and are a secondary falt

I went ahead and changed the plugs. As part of that I swap the coil from cylinder 1 to cylinder 2. Problem should move if the coil has a problem. I found that the remaining problems were related to the oil change I did. LOL When I changed the oil a couple days before I apparently did not tighten the oil filler cap on the valve cover fully. Found it was loose. After posting on another board I found a couple responses said that the engine sounded like it was running lean, they said check for vacuum leak, fuel delivery, and CCV. Apparently the a good seal on the cap plays and important roll in crank case ventilation. Always amazes me how simple things like that matter so much to the electronic control systems.

Been a couple days and I am error code free. Guessing the coil problem was a worn plug. That I had seen before the oil change but was not causing the service engine soon light to illuminate.