1989 300se check engine light on only when brake pedal applied
 

I have a 1989 300se. The first time I step on the brake pedal after starting the car the check engine light comes on and won't go out until I turn the car off As long as I don't step on the brake pedal the check engine light will remain off. I have driven down the interstate for 1 hour without stepping on the brake pedal and the check E L stays off.As soon as I exit the interstate and apply brakes the light comes on and stays on until I turn the car off.I restart and once again no check engine light will come on until I hit the brake pedal. Has anyone encountered this problem before? I placed the post also on Mercedes forum with no luck yet. thanks again.

How did you get the car in gear to drive without hitting the brake pedal? I'd assume you wouldn't even be able to drive at all without the CEL because you need to depress the brake to even get the car in gear.

How funny would it be if someone had the instrument cluster out and re-installed the exterior bulb failure lamp into the CEL socket. Maybe you've just got a brake light out?

On my 1989 300se.I can start the car in park. No need to depress the brake to start the engine.like I said.the cel comes on only when I apply the brake.car has not been to a shop.bulbs all work.if I start the car no light.once I apply brake pedal light comes on and remains on until I shut her down.I can restart in park and put her in drive on flat ground without touching the brake and drive with no check engine light.but once I apply brakes light comes on?

My 89 300se does not require me to step on the brake pedal to put it in gear.maybe the newer models.I can start in park .yes, I do put my foot on the pedal to shift into gear but what I am saying is that I do not have to.I can shift into drive and take off without depressing the pedal.my problem is the cel comes on only when I touch the brake and remains on until I shut her down.I start in park.engine running,no light.touch brake.cel comes on? Thanks

I found out only the 90-91 had lockout transmissons, so you had to depress the brake, to put the car in gear. no so on the earlier models. 88-89.

only on 90&91n models have lockout transmissions
 

you need to depress the brake pedal to shift into gear on the above models.my 89 you can shift into gear without the key in the ignition or without touchihng the pedal. still have problem with check engine light on onlyl when brake pedal is applied. I think it maybe some sort of a vacuum probem, not with the booster but maybe the abs system. although my abs light does not come on, only the cel.

read post #3 again. pull the cluster and look at the lights. seen it lotsa times before. good luck, chuck.

check engine light on when brake pedal applied
 

the cluster has never been out of the car. the lights all work in the cluster. check engine light comes on only when I touch the brake pedal and stays on. Mercedes 300se didn't have the lockout transmission where you had to depress the brake pedal. search 300sel check engine posted 01-09-2007 by mullet 904

CLUSTER HAS NEVER BEEN OUT OF THE CAR. BRAKE BULBS ARE GOOD. FLUID LEVEL IS UP, PADS AND SENSORS ARE OK

another possibility is an incorrect 2 filament bulb installed into single socket where a single filament should be

cluster has never been out. never been touched my anyhone be me. all lights work in cluster pane. cel come on only when brakes applied. verifying that the lights all work. I think it may be a vacuum plablemno unuaLLY PROBLDEM WITH BOOSTER.fluid topped off. ALL BRAKE LIGHTS NEW

AGAIN, IT'S NOT A VACUUM LEAK. you have to look for an electrical problem causing the light. it's in the wiring, cluster, somewhere. it's not the engine or brake booster. give it to someone who knows mb and we'll get the answer. you have tunnel vision about the problem. good luck, chuck.