Drive cycle 1996 C280
 

I recently had some sensors replaced for OBD2 and have driven the car about 200 miles but at the inspection station the monitors are still coming up "NOT READY". I was told to find out Mercedes drive traces or cycle procedure and can't find them anywhere online. I really need the car to pass inspection. Thanks.

when i have had that issue on customers cars, the only fix i found was to reset the DM module. to reset isn't simply clearing the codes, but a hard reset using factory diagnostic computer. this procedure seems to work everytime i have had problems like yours. where are you? if you are close i could do it for you

Thanks. I'm in Long Island, NY.

200mls on freeway won't get job done.but 3 days of driving around town if the injection system is running corr.will.

sorry, i am in orange county california, definately try what david says, hopefully that will do it

So how did you fix the problem>
 

So how did you end up fixing it? I am currently with the same problem so i would really appreciate if you share your solution :) thanks!

The problem with posting onto a post from the Archieves is they are old post...
Do you see you are asking a post 3 years old??

true
 

But i just hoped he may receive an email about my reply and he might come back and post a reply... is it wrong for a fella to be hopeful?

Not at all...Hope is Good ...just a Forum suggestion to help get you on the right track , only b/c I noticed you are a new poster..that's all.

If you simply post a New post, I am sure you will have a much better shot at recieving an answer than to hope a guy from 3 years ago was even still here...


No problem...Excuse me for pointing that out for you..........

I would say this is the answer right here.

To start with.........readiness isn't about how far you drive but how & what speeds you drive.

You must drive at low speeds (5-6 miles) 25-30MPH w/o load, means a/c & electrical equiptment OFF. Then at 50-55 MPH for 10-15 miles & then left at idle for 5-10 minutes.

Right ..which is why some can take weeks ..depending on the drivers style.

Here is a drive cycle criteria for self test verifications.

The OBDII drive cycle begins with a cold start (coolant temperature below 122 degrees F and the coolant and air temperature sensors within 11 degrees of one another).

NOTE: The ignition key must not be on prior to the cold start otherwise the heated oxygen sensor diagnostic may not run.



1. As soon as the engine starts, idle the engine in drive for two and a half minutes with the A/C and rear defrost on. OBDII checks oxygen sensor heater circuits, air pump and EVAP purge.

2. Turn the A/C and rear defrost off, and accelerate to 55 mph at half throttle. OBDII checks for ignition misfire, fuel trim and canister purge.

3. Hold at a steady state speed of 55 mph for three minutes.


OBDII monitors EGR, air pump, O2 sensors and canister purge.



4. Decelerate (coast down) to 20 mph without braking or depressing the clutch. OBDII checks EGR and purge functions.

5. Accelerate back to 55 to 60 mph at æ throttle. OBDII checks misfire, fuel trim and purge again.

6. Hold at a steady speed of 55 to 60 mph for five minutes.


OBDII monitors catalytic converter efficiency, misfire, EGR, fuel trim, oxygen sensors and purge functions.



7. Decelerate (coast down) to a stop without braking. OBDII makes a final check of EGR and canister purge.


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Bumping this post. I've been failing smog for years due to "monitors not ready". In California (before 2011) I had to take the car to the state referee and they would override and give me the smog cert. And that was with 3 monitors not ready (EGR, secondary air sys, and catalyst).

Now the max is 2 monitors not ready. I'm going to try the above cycle and hope I get one of them going. I have an OBDII scan tool to check. Hopefully I get one of them running before my $165 diagnostic appt at the dealership on Thursday. :eek:

Finally what part of the cycle gets the secondary air sys monitor to run?

Thanks!

You'll see I have the same situation with the same readiness monitors. You'll see my threads regarding the problem but it's still unsolved after over a year. What I've noticed for sure is that my secondary air runs fine at cold startup and there is no blockage. However, the check for the secondary air, which occurs by running the secondary air momentarily at the first idle after the car has entered closed loop, does not run. I have not gotten any input from anyone as to why that won't run. I'm not focusing on the catalyst monitor as I believe that will only run after the secondary and egr monitors run. What I don't know is if the egr monitor needs to run before the 2ndary air monitor. My guess is that it should not. As I have access to another c280 (1994), it runs the 2ndary test at the very first idle after warmup every time. Please let me know if you have any success. My dealer and independent were not able to determine the problem.

I also believe the specificity of the drive cycle is not applicable in our situation. My monitors set in the past easily and without all of the drama of these specific drive cycles. I just tried to drive in varying situations, and it worked. There would have to be a reason as to why it would have gotten more difficult if not impossible to get readiness on these. 2ndary air monitor test is simply, car enters closed loop (warmed up) and then runs the pump to see that the 02 reads lean. I'm thinking wiring/CAN or ECU. Starting in 96, you can't simply swap ECUs as they're VIN Coded. Supposedly for theft protection. Sure, someone's going to just steal the ECU and not the whole car.:rolleyes: I've switched out the Diagnostic Module as that is not coded and that appears not to be the problem as in another car, my diagnostic module works fine.