Maintenance Advice

[JollyRogerX]

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.

[stv840]

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

[JollyRogerX]

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.