I decided I wanted to know when, how often, and how long the MDS system works on my RT, so I hooked up an MDS indicator light. Easy to do. I used an illuminated rocker switch for the light. This way, when it is on I can monitor MDS activity and turn it off when I don't want to monitor. The most difficult part of the installation was routing the wires into the car and finding a suitable mounting location. I ended up putting it under the ignition key. It is fairly inconspicous, easy for the driver to see and does not glare at night. What I have found after several test drives is that MDS doesn't even work until the engine is at about 130 degrees. It is extremely sensitive to throttle application. The slightest touch and it goes off. The latest it shut off when coasting down was 20 mph. Accelerate and just take your foot off the throttle didn't always make it come on??? On the highway it is very predictable and works almost continuously on level ground at cruise above 40-50 mph. I don't know all the parameters required to make it work, but by testing and trial and error I know the following have some bearing on when the MDS is active and when it is not. They are, engine oil temperature, engine oil pressure (haven't seen it work with less than 45 PSI oil pressure), gear selector position (must be in "D"), coolant temperature (haven't seen it on when temp. is below 130 degrees), vehicle speed, Manifold Air Pressure (MAP)/throttle position, and perhaps outside ambient temperature. There may be more, but most of these I am fairly certain have some impact on how/when the MDS works. Today I think I broke the code on low speed operation. It must be in "D" and 3rd gear to make it work between 20-28 mph. About 28 mph it shifts to 4th and immediately shuts off. I could not get it to come back on in 4th until about 34 mph, but slow back down below 30, back shift to 3rd and then put it back in "D" and the light comes back on. Kinda interesting to tinker with. I think a little experimentation will allow me to figure out how to get better in town mileage, now that I know for sure when the MDS is working and when it is not.

 

That is very interesting. I would like to hear more on what you encounter in the future with the testing.

 

Interesting. Did you pickup the signal from one of the coils?

MikeyB

 

MikeyB,
I picked up the signal at the PCM. It is tapped into the No. 4 cylinder MDS solenoid power lead.

 

Magnuman,
I don't have a shop manual for the RT. So can you give the the cylinder layout? I would like to do the same. In one of the electronics catalog there is some companies that make custom indicator lamps and they can print letters and icons. I will check to see what the cost would be to have 'MDS' printed on one.

MikeyB

 

MikeyB,
You need to tap into the 18 gauge brown/light blue stripe wire on plug C1 (the top plug) of the PCM. This is the power wire for the No. 4 cylinder MDS solenoid. It is the easiest one to get to because its in the top plug. If you need to verify the wire with a multimeter, it goes to pin 28 of that plug, which is (when the plug pins are facing you) the far left pin on the second to bottom row of pins. Before fooling with it, make sure all power is off. If you want to check out my "how to" on the DodgeMagnumClub forum, here is the thread:
http://www.dodgemagnumclub.com/board...ad.php?t=11575
It will give you the full blow by blow with details and a few pictures. Hope this helps.