S420 fail smog test

Hi Mercedes fan, I have a 1996 S420 Benz, it failed the smog test twice. Right now it at the Smog test and repair station, being diagnose. The smog guy said he need to
drive the car for atleast 150 to 200 miles, so he can get the monitor or engine light to come on. Have anyone have this problem. I need to get the smog pass, so I can register the car.
Thanks in advance, Dara
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What part of the test failed?? Do you have a print out of the tailpipe readings? A little more info WOULD help!!

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I think it have something to do with OBD, which require me to drive certain amount of miles. Due to someone turning of the engine light.

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Dara wrote:

This page will have some instructions (I think...):
http://www.europeantransmissions.com/Bulletin/merctechlib.htm
br, syljua
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I believe the OBDII drive test does not apply to a 96 MB. A 96 should be OBD. OBDII started in 98?

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Karl wrote:

Wrong, '96 is OBDII. I think '95 may have been also.
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My 1995 SL320 is also OBDII compliant
Peter

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Dara wrote:

Let me guess, they failed you because your Check Engine Light was on when they did the test. There is a Mercedes Service Bulletin about this. On 1996, and some other model years, the Check Engine Light illuminates whenever a device is successfully connected to the OBDII port. This lets you know that the device is actually plugged in. This does not indicate a failure. Later versions of the OBDII spec disallowed this "feature".
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Hello Dara,
Your vehicles might be failing from an OBDII readiness problems. Here's the explanation. Note: This info is from SmogTips.com. http://www.smogtips.com .
If you own a 1996 or newer vehicle you more then likely own a vehicle which is equipped with an On-Board Diagnostics system called OBD II. The OBD II Diagnostic system is designed to monitor all aspects of your engine's emission conditions and report this information to a central database within the OBDII computer. This information is processed and checked against the computer's pre-determined values for various inputs levels and performance patterns of your vehicle. If any problems are found, the computer will determine whether to alert the driver or not. If a decision has been made to alert the driver of an emissions problem, the "Check Engine" or "Engine Malfunction" light will illuminate on the vehicle's dashboard. In more serious emission conditions the computer may even begin to rapidly flash the "Check Engine/Malfunction" light indicating to the driver, that the vehicle needs immediate diagnosis/repair attention.
Now here's what the smog test has to do with the OBD II system. Your vehicle is equipped with an OBD II computer AND a link to connect the OBD II computer to a Smog Check Analyzer or Data Scan Tool (available at most auto part stores). The OBD II link relays all "Check Engine" conditions along with stored Trouble Codes within the central database, to the smog machine during the time of the smog inspection. If any codes are present which cause the Check Engine light to illuminate either regularly or intermittently, the vehicle fails the smog inspection. Here's the tricky part, not all computer codes illuminate the Check Engine light, yet will fail a vehicle during the smog test.
In fact I can say there are two types of codes, bad codes and good codes. The good codes are the "Readiness Flags". These Readiness Flags indicate that certain emissions systems which the OBD II computer has been monitoring have PASSED the test, indicating that those systems are working properly. Then there are the bad codes. The bad codes are actual "Trouble Code". These codes indicate that the OBD II computer has detected a problem with in the emissions system. The Trouble Code will specifically indicate the component and problem which was found. Newer vehicle's have very complex codes in the thousands.
A vehicle will fail the smog inspection if the proper "Readiness Flags" are not set. A vehicle will also fail the smog inspection if any "Trouble Codes" are present. So it is possible for a vehicle to fail the smog inspection without the "Check Engine" light on. "Readiness Flags" do not cause the "Check Engine" light to illuminate, but may cause a vehicle to fail the smog test.
The repair in this case involves extracting all stored trouble codes and readiness flag readings from the OBDII, and inspecting the emissions systems which are indicated. If this has already been done. The next step involves driving the vehicle through 2 or 3 "drive cycle" in order to set the proper "flags". Drive cycles vary per vehicle - usually 1-2 weeks worth of driving is enough.
I hope this information is helpful to you. If there is anything I can help with in the future, don't hesitate to e-mail.
For more information you may want to locate a reputable smog service center in your area by simply typing in your zip code in the Smog Shop Locator search section at www.smogtips.com
Sincerely, Alec - SmogTips Support
Dara wrote:

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<snip> I hope this information is helpful to you. If there is anything I can

Very interesting! thanks,
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