BayStateMB

Hello all - newbie here. I am hoping for some good advice from the seasoned members of this forum. [As a preamble, I did a search of the forum using the indicator words in the title above before starting this thread and found only vague references within a thread on the rear plate/tag lights.] My wife drives an 05 that developed a malfunction indicator for the rear left taillight. The bulb was burnt out so I went to Autozone and found the apprpriate 5w bulb consistent with the manual. I replaced the burnt out bulb and everything works great - both functions for the tail light and as the brake light. Unfortunately, the malfunction indicator still continues to state 2 malfunctions - "tail light left" and "back-up tail light left on". It is a harmless but irritating reminder so that I am hoping for some guidance on how to reset it without having to go to the shop. If there is no other way without going to the dealer, it will be good to learn that as well. Thanks in advance.

e1000

It should be a 25w bulb. The ones on the bottom row are 7528 (similar to 1157's) and the reverse light is 7506. Try those. The errors will clear when whe computer believes there is a properly operating bulb in the socket.

BayStateMB

Thanks e1000 - That is interesting information because the manual states: P 21W (position #8 on the figure drawing, top of the taillight). I matched an exact Sylvania 7506 21W long life light bulb to the one that was burnt out. I wonder if the bulb type that is being used has changed between model years?

e1000

nvm, you're right, 21W. The bulb at the top of the tail light should be a 7506, 21w bulb, but should not come on as a running tail light, only for the brake light.

BayStateMB

I guess I am at a loss, then. As far as I can see, the tail lights are lit symmetrically when the light switch is turned on. The brake lights appear symmetrical when the brakes are applied. I assumed the message should have gone away automatically after the bulbs were replaced - like they did when I replaced the side markers bulbs and city lights.

I wonder if it had to do with me pulling out the housing so that it is easier to replace the bulbs? I disconnected the wires from the housing for a moment because the space was tight if I just tried to squeeze the bulbs in. However, I reconnected them easily with a nice tight fit.

Unless any other ideas come up, my wife will just have to live with it until we need to go to the shop then. Bummer.

03MBC320

^^ i have a 2003 C320 and believe i have a similar problem, unless its usual that my left tail light "goes out" about every 2-3 months?
every so often i'll get malfunctions: Check L Tail-light, then "Substitute tail light on", and when i check, the lighting seems fine (although that may be because the "substitute tail light" is on)
this has happened a few times, and every time i put a new bulb in the warning goes away for a while, when i brought my car in to mercedes because of the leaking radiator/contaminated tranny fluid i asked them about it and once the service advisor began talking i saw dollar signs rolling through his eyes so i told him forget it
as said above be sure that the bulb is correct wattage and properly installed, i put some bulb grease on the tip of it this time and hopefully that helps but goodluck interested to see what the problem is

BayStateMB

Thanks and I'll try to remember to circle back when we eventually get to a shop for the next service. By the way, I did place some bulb grease.