Neither the center electrode nor ground electrode look very worn so gap should be as new at .040 or 1 mm. I cannot see why these plugs would cause a CEL so perhaps OP could comment. Sure change them but were they the cause of the CEL?
Sorry about that, I should have been clearer. The CEL turned out to be due to a faulty relay switch in my brake pedal. While the car was in the shop they did a thorough inspection and that's how I found out that I needed to change the plugs.
The funny thing is that a few weeks ago I took my car into my local Autozone and had them use their generic code reader to tell my why the CEL was on. The guy pulled P0140 as the error code, which is something related to emissions - either an O2 sensor or a malfunctioning MAF sensor. After doing a little research I estimated that it would end up costing between $300.00 to $600.00 to repair, so I budgeted $600.00, took it to the shop yesterday and crossed my fingers. The guys called me an hour and a half later to tell me that the CEL was due to a faulty relay switch that sends the signal from the brake pedal to the computer. He then told me that my rear brake rotors and pads needed to be replaced (which I knew, I was just procrastinating on doing the brake job because brake dust is nasty and I hate doing it) and that I was still running the original spark plugs.
Now, I do all the maintenance on my cars because I don't like paying someone else to do something I can do myself. He said it would be $200.00 to change out the brake pedal sensor and $350.00 for the brakes. I did some quick math in my head and realized that was a pretty good price for the brake job (did I mention that I had been putting off doing the brakes because brake dust is nasty?) and I really didn't want to mess with the brake pedal relay. So far so good.
Then he tells me he can change out my plugs for $192.00. I almost laughed out loud into the phone. After regaining my composure I politely declined, told him to fix the brake pedal relay and do the rear brakes. I then spent $30.00 on a new set of spark plugs and when I got my car home yesterday afternoon I changed them in about 20 minutes,
All in all I think it turned out to be a good day. I was planning on spending $600.00 to have the MAF sensor replaced and I ended up spending $590.00 to get a rear brake job, replace a faulty brake pedal relay switch and change my spark plugs.
Long story short (too late) don't believe anything you get from a generic $20.00 code reader. If your CEL comes on take it to someone who has a code reader calibrated for a Mercedes.
Oh, and change your damn spark plugs!