08-13-2005, 07:45 AM
Join Date: Jul 2005
I think M.D.S. reset is required in some cases. I have previously disconnected the battery with no M.D.S. ramifications; however, after a recent disconnect, my M.D.S. was inoperative. It seems to be a hit or miss thing. I am not positive the problem was related to the battery disconnect; I am positive M.D.S. wasn't working.
I hardly ever reset my average milage display. Normally, it hovers around 18. Recently, it dropped to 14. No change in driving habits. I reset my MPG reading and only got 17 mpg over a 30 mile trip using cruise control set at 60 miles per hour (it should have been 24 or so). I followed the MDS reset procedure and, PRESTO, my average m.p.g. jumped up to its historical levels.
My 05 300C owner's manual & service manual make no mention of this; however, the 06 owner's manual does. The second
edition of the 05 Grand Cherokee does mention it. It seems strange M.D.S. reset would be required on some of these extremely similar powertrains and not on others.
If your mileage recently dropped with no change in driving habits, try the following procedure.
No flaming required, I am not saying I bought this car with mileage in mind.....I am saying that when there is a drastic drop in mileage that a very simple reset solves, people need to be informed (especially since no documentation from Chrysler refers to the reset, at least for the 05 C models).
Procedure (as copied from another forum):
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.