A week ago the check engine light comes on and my console display stops working. The display tells me to get service. I also see that my passenger side headlight is out. Since I have an extended warranty I take it to the dealer.

They run a diagnostic and I have misfires on both banks. The vehicle has under 50k miles but the dealer states that I must first change all my plugs for $845 because that is required every 5 years and they have no record of plugs being changed. I call my mechanic that serviced the car when I was living in another state and he tells me that plugs have not been changed but that it is most likely a bad coil.

This is late on a Friday, dealer does not have plugs so they will be ordered. When I ask about the display/light it hadn't been checked since my wife didn't mention it when dropping off the vehicle.

As of yesterday "all parts were in" and cluster is fine. Service adviser said headlight is working but a bit dim and probably near end of life. They were putting in plugs, would clear codes and test on Monday. I'm not too happy a week later without a definitive diagnosis. I cam imagine a text Monday that coil is bad and they need to order parts...

How can display totally go off with headlight also and then just start working again? I turned the vehicle on and off several times over an hour and display would not function. Any ideas out there as to what is happening?

display prolly worked fine when dealer checked...

very likely could be the ignition module. keep us posted.

I'd never do plugs based on years; they are strictly a mileage replacement item. It's not like they have rubber parts or anything that wears out with age.

It also makes little sense to remove the original coils to do the plugs, then put the old coils back on. That's just begging to introduce issues that you may not have now. With misfires on both banks I'd blame the ignition module first. It's something you can replace yourself in literally 5 minutes, mounted right on top of the engine.

If by "display" you mean the entire gauge cluster's backlight doesn't work, that's a common problem and there are a few fixes. Your 2006 should be under the extended 10 year warranty all CL and S-classes get for the cluster. It's a free replacement. For cars outside that timeframe you can get it fixed for around $200 or DIY with a $40 part from ebay.

Display error was not a backlighting problem. The entire display except speedometer displayed no information, just error message to have it serviced.

Just got car back but adviser was gone. Plugs were changed, codes cleared, and all appears o.k. Still no word on what could have caused light and display to both be out.