FAQ: Is MDS Reset Required after Battery Disconnect?

[ricardo]

Manual says MDS has to be reset every time battery was disconnected and directs to contact dealer to do this. Can this be done without going to a dealership?

I am concerned about MPG performance and started to suspect dealership disconnected it while the was sitting on their parking lot and then forgot to do the reset. I am getting around 17 mpg on highway and 14.7 in city. The car has 1k miles on it.


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2006 Bright Silver 300C
Everything, but Sirius and rear seat DVD

[arnoldw]

That's a new one There's no mention of that for the 05's.

[5point7]

I wonder if you are thinking MDS rather than the BAS/ESP.

When the battery is disconnected, you need to reset your the ESP by turning the steering from clock to clock...and the one touch windows need to be reset as well. There is info on this in the Tech/FAQ.

[ricardo]

Originally Posted by 5point7

I wonder if you are thinking MDS rather than the BAS/ESP.

When the battery is disconnected, you need to reset your the ESP by turning the steering from clock to clock...and the one touch windows need to be reset as well. There is info on this in the Tech/FAQ.

I am not confusing ESP with MDS. I am concerned about the milege I am getting per gallon and thought MDS was not working right. With all other cars I owned, fuel efficiency was about the same as advertised or better. This one is much worse. Then I bumped into a short section about MDS reset in the in the manual and recalled that I saw a number of times cars in dealers' showrooms with battery disconnected.

[5point7]

Interesting...what page in the manual? Maybe post a pic?

Anyone have an 06 service CD?

My mileage has been 13 to 14 since I bought it, and though my foot is a little heavy....even if I put my EVIC display on the mileage indicator..I still only manage maybe 14.3 (trying hard to be get max mileage).
I have 13,500 on her now so she's well broken in.

[Mr. Redbird]

I also average 14-16 city miles per gallon in my 300C. I double check this every time I fill up. The car is 1 year old with 7,000 miles on it. I don't drive it especially hard. I don't think the car gets the mileage stated on the sticker but to be honest I enjoy driving it so much I don't care.

["C"Bandit]

Yep my 06 manual says the same thing about the MDS. Dealer must RESET it after a battery disconnect/reconnect.

[ricardo]

Originally Posted by 5point7

Interesting...what page in the manual? Maybe post a pic?

Anyone have an 06 service CD?

My mileage has been 13 to 14 since I bought it, and though my foot is a little heavy....even if I put my EVIC display on the mileage indicator..I still only manage maybe 14.3 (trying hard to be get max mileage).
I have 13,500 on her now so she's well broken in.

It is page 222 of 2006 User Manual. It does not say much more, but I will try to scan and post the page tonight (if my new multifunction scanner works - some problems with driver configuration).

Last evening, I got over 1,500 kms (just under 1,000 miles) and MPG performance suddenly increased almost to the expected levels of 17 mpg in city and around 22 mpg on highway at around 82 mph. Even on city streets at 32-35 mph it was around 21 when I got into a green wave.

Could it be the end of break-in period? I am planning to cancel service appointment for tomorrow which I insisted upon in order to reset MDS due to poor MPG performance.

I was constantly resetting computer yesterday to monitor the immediate MPG performance with various driving styles and not to be affected by averages. I tried to use the numbers described in threads about installing MDS monitoring light by sharply accelerating to the levels and them sharply changing to steady crusing at slightly lower speeds in order to provoke MDS and provide clear signal of reduced load. Should be careful in traffic though as the process is a bit distracting.

This morning I mostly drove on a freeway, which in our metropolitan area is not too free at rush hour. I saw averages around 17.8 mpg with some stop and go. It went up to 18.1 mpg when I have got on a more clear stretch. I have not done any resets since last night, but averages are still volatile enough to be affected by immediate readings.

I do not know what exactly triggered the change, the 1,500 kms milestone or my attempts to provoke the system and trigger it to be more responsive. It is computer driven and is likely to be adapting. Bringing the system a bit out of balance may help it it tune to your style.

[ricardo]

Originally Posted by "C"Bandit

Yep my 06 manual says the same thing about the MDS. Dealer must RESET it after a battery disconnect/reconnect.

Yep! After talking to couple service advisers at different 5 star dealerships, I came to conclusion that they have never heard about this one!

[magnuman]

ricardo,
For 1000 miles your in town mileage is not that bad, but the highway mileage seems a little low. My mileage has been continually increasing as I put more miles on. I am at 7000 miles now and highway mileage has increased about 5 mpg since new. Also you may want to check TSB 08-013-04. It has the MDS reset procedure in it. This TSB has been superceded by -04A, which eliminates the portion that deals with MDS reset. There is no reason indicated why it was eliminated though, but the next to the last step calls for use of the StarScan tool to clear all DTC's. Basically though, it says:
1. You need a fairly long, open, safe, straight road for a WOT run to about 35 mph.
2. Get engine up to operating temp., engine running and car stopped put selector in "D", move it to the right until in "1".
3. Turn off all electrical accessories (except lights if needed).
4. WOT run to 4500 RPM (about 35 mph), immediately remove foot from accelerator and do not depress the brake, let the vehicle coast with the throttle closed until the vehicle speed is again at 35 mph or lower.
5. Stop vehicle and place in "Park", verify all instrument cluster warning indicators are off.
6. Cycle ignition switch "Off" and back "On", but do not immediately start engine.
7. Hook up StarScan and clear DTC's
8. MDS calibration is now complete.

If you have access to a Scan Gauge, you can clear the DTC's with that. The only cost about $125, and are well worth the investment, IMO. You could also do my MDS "On" indicator light mod. which will let you know when the MDS is active. See it at: MDS "ON" Indicator Light
Hope this helps.