[ericahn]

I have been struggling to solve the problem of my 1996 SL500 OBD not getting ready issue for smog test pass for long time.
Numerous times by local mechanics I have been told to drive more, drive more, and go thru MB Drive Cycle. I went thru all these many time with risk of getting pulled aside by Police, because the Drive Cycle procedure is so tricky in maintaining certain speed for certain time. Anyway, it didn't work for me or maybe I did not try hard enough repeatedly. I concluded it ridiculous and decided to find an exact reason why my OBD does not complete the test cycle. And still trying to figure out. My diagnostic scanner does not show any Error code.
I found it is not only my car with this problem and so I put this post up here.
What I like to know logically are;
1. What device or parts of vehicle connected to this OBD to run the test besides the so-called computer in the Engine Management System box.
2. Will this happen when any of the instrument panel warning light bulbs are out?
3. Any of sensors other than O2 sensors (I had them all replaced) in the trunk may cause this?
4. Before replacing the computer(I plan to buy off the junk yard if I can find the same wrecked car), is there anything I need to check first.
Anyone out there has valuable information, I would greatly appreciate your help. Thanks in advance.

 

[Kajtek1]

Each part of driving cycle is testing different components/sensors on the engine management.
I went via frustrating experience last year (first time had CEL on MB) when after driving 250 miles the car was still not ready.
Than I pulled out copy of driving cycle and in my case it was the habit of driving immediately after engine start that was making the situation.
Following morning I start the engine and let it idle on the driveway.
5 minutes later it was ready.

 

[ericahn]

Good for you, Kajtek1, I enjoyed your post.
I remember seeing some movies, in which someone bang the soda machine to make it work. Bang, and a soda can came out. Wow.
Here I have gone thru all kind of Drive Cycle, idling 15 minutes before starting Drive Cycle, etc, etc, etc, etc,
I still want to get down to fundamental reason why this happens to 1996 models. The concept of Drive Cycle does not seem to be the right approach to solve this problem to me. I will keep looking into this until I find a way to resolve so it does not happen again.