[SteveSchwab]

@blazz81 did you solve the MDS stuck in “on” mode, or determine a test for it?

I replaced the solenoids, put in fresh oil, and had issues with a pinched oil temp sensor. After fixing the wire, I lost all throttle response. After clearing codes and resetting the PCM, I had a solid 20 mile drive running great. Then failures started on every drive. I tested each solenoid, and they all seem to turn on and stay on.

I’m thinking I have a bad PCM at this point, but would like to know how to test for the MDS off signal to be sure.

Thoughts?

 

[SteveSchwab]

I found this document related to MDS failures and tests:

https://www.autonerdz.com/yabbfiles/Attachments/MDS.pdf

Since I am not getting any cylinder reactivation codes when the MDS solenoids are “on” and the engine is running rough under load, can I assume that my PCM is not running the test correctly, and is the likely problem?

 

[SteveSchwab]

Update: I found a resource for a new PCM (Mark at wranglerfix) but held off on placing the order until I could get the failure codes again.

But before I drove, I tested every possible voltage level and solenoid in my driveway using my scan tool. The TPS voltage test failed to get a reading, and the MDS solenoids would turn on, but not off, until I backed out of test. I reset the PCM, cleared adaptations, and drove off.

After about 30 miles of no issues, and the MDS working as designed, I stopped at an auto parts store to pick up a degreaser and shop towels. Drove another 20 miles with no issues, then stopped for a haircut. Drove another 10 miles home with no issues.

I suspect I still have a bad fragment in the PCM, but am going to drive until I experience a code.

I will try to remember to report back in the future.

 

[SteveSchwab]

Update: I got a stumble and loss of power on my next morning drive. Pending codes for cylinder 7 misfire and MDS failed to deactivate. I found that my scan tool has active monitoring for each of the MDS solenoids. I cleared codes, reset ECU, then continued my drive. Stumbling and misfire shortly after getting up to speed. This time two MDS solenoids failed to reactivate.

I stopped, cleared codes and reset ECU again, then restarted my drive in tow mode. After driving about 20 miles in tow mode, I went back to normal mode and drove the 20 miles back home with perfectly performing MDS solenoids.

I believe that I experience MDS issues before the oil is up to temperature. I believe the short met have damaged the oil temp sensor, and MDS is initiating before the oil temperature limit is met. I am going to replace the oil temp sensor and hope to report back with results.

 

[SteveSchwab]

Update: Turns out that the wire I shorted was for the coolant temp sensor under the A/C compressor. I learned this after I received the oil temp sensor, and I will return it.

But I replaced the coolant temp sensor because I broke it on removal, with one I bought from a local parts store. Another $20 error.

MDS still tries to engage when the oil is too cold, and one or more solenoids stay open causing a misfire. I am convinced my issue is in the PCM, as it seems to engage MDS before all conditions are met. I will order the PCM from Wranglerfix and report back with results.

 

[Don Fox]

SS:
We have seen here that the oil sender and oil temp sender can cause grief if they are flaky, or out of spec. You might consider replacing them just to rule them out. BTW, our Durangos and most Dodge vehicles prefer oem sensors. Just a thought.

Don

 

[Polaridoo]

Steve - just found this thread while experiencing the exact same issues as you with my 2005 Hemi Grand Cherokee. Did the new PCM fix your issue?

 

[SteveSchwab]

Sadly a new PCM did not resolve the issue, so I returned it.

I found an article about Hemi’s that said the vehicles with MDS have a different camshaft, the MDS solenoids, and an oil temperature sensor. If it is true that these are the only unique parts, my issue has to be the oil temp sensor.

I have a new OEM oil temp sensor in hand, and will install it soon.

 

[Polaridoo]

Thank you for the update. When the weather warms up a little bit more and I can get it to fail, I am going to try to back probe the MDS wires to see if the PCM is commanding 12 volts when it shouldn't be. I am also going to plug in my code reader and see if I can monitor water and oil temperatures next time I drive it. I am 99% certain I have the same problem you are having. Everything you described is the same as my hemi.

 

[Vynh]

Sadly a new PCM did not resolve the issue, so I returned it.

I found an article about Hemi’s that said the vehicles with MDS have a different camshaft, the MDS solenoids, and an oil temperature sensor. If it is true that these are the only unique parts, my issue has to be the oil temp sensor.

I have a new OEM oil temp sensor in hand, and will install it soon.

Did the oil temp sensor fix it? It’s been a few weeks.

 

[SteveSchwab]

Did the oil temp sensor fix it? It’s been a few weeks.

Sadly, no.

I am stumped.

 

[Vynh]

Sadly, no.

I am stumped.

Me too - I'm experiencing almost identical symptoms, only on #4 - and only #4. So for, I replaced all 4 solenoids (since I was already in there), and I had to replace #4 again. I did have some bad coils, so I replaced all 8 coils and 16 plugs. I also flushed and changed my engine oil and filter.

I cleared the code with my scanner and drove for 1200 miles with no problems, then it started again. I did notice that it happens only when I'm not in cruise control. When I'm in cruise control, it seems to work fine (going to test that theory later today). I wonder if the throttle position sensor plays a part?

 

[SteveSchwab]

I experience failure to deactivate MDS only when the engine is cold. I do not experience any MDS failures or misfires once the engine is at operating temperatures.

My theory is that the oil is too thick to create sufficient pressure to deactivate the solenoid until it is warmed up.

I run in tow mode until the coolant temp gage shows the engine is fully warmed, then I turn it off and the engine runs flawlessly.

I suspect that a bad sensor or wiring circuit interference is causing an electrical signal to the ECU to be out of spec. What I don’t understand is why an out of spec signal allows the MDS to activate at all. It would make more sense to me for the system to fail to activate when one or more conditions and/or signals was out of spec.

Also, it seems that the only sensor unique to MDS in my vehicle is the oil temp sensor. I would expect all other sensors to throw a DTC when out of spec. I am considering buying a multimeter to test the oil temp sensor circuit but am not sure what would be considered a good result.

 

[Vynh]

I experience failure to deactivate MDS only when the engine is cold. I do not experience any MDS failures or misfires once the engine is at operating temperatures.

My theory is that the oil is too thick to create sufficient pressure to deactivate the solenoid until it is warmed up.

I run in tow mode until the coolant temp gage shows the engine is fully warmed, then I turn it off and the engine runs flawlessly.

I suspect that a bad sensor or wiring circuit interference is causing an electrical signal to the ECU to be out of spec. What I don’t understand is why an out of spec signal allows the MDS to activate at all. It would make more sense to me for the system to fail to activate when one or more conditions and/or signals was out of spec.

Also, it seems that the only sensor unique to MDS in my vehicle is the oil temp sensor. I would expect all other sensors to throw a DTC when out of spec. I am considering buying a multimeter to test the oil temp sensor circuit but am not sure what would be considered a good result.

What your saying makes a lot of sense - thicker oil would indeed slow the deactivation of the MDS lifter. Unfortunately for me, the last time it occurred was after I had already been driving for almost 2 hours - already operating temp for quite a while. But, I will try that to see if it works for me.

What I would really like is an explanation about how the PCM determines if the solenoid deactivated. I have a theory:

Since the coil of the solenoid measures about 10 ohms at 68 degrees F, the voltage across it should be near 0.0 when it's not activated. I suspect there is a circuit inside the PCM that reads that level after the reactivation command. If it reads something over some level (don't know what that is), then it thinks the circuit is still active. A poor or intermittently open ground wire on that solenoid would cause that symptom since the low resistance through the coil would not be pulling it down to ground. But that is just a theory, as I'm traveling and cannot take my intake off at the hotel.

 

[Polaridoo]

Just thought I would update the thread with the latest. I took my Jeep to the dealer for a diagnostic. They kept the vehicle two days and ultimately said it probably is the MDS wiring harness. They wanted $1,800 to do the job. Sadly, they are not willing to guarantee their diagnosis. I don't want to shotgun anymore parts or money at the jeep, so I am more than likely going to find a tuner and just turn MDS off.

 

[blazz81]

Hello everyone I made this post quite a while ago I own two durangos both are 2006 limited the one I was having problems with I ended up just disconnecting the oil pressure sensor without that reading it will not go into 4 cylinder mode. when time comes to get it inspected I just simply plug the sensor back in and drive around for a day or two with tow haul mode on.
But now my second durango is doing the same thing which brings me back to this form I wanted to see if anyone has replied and I see that there has been.
From all the research that I have done and all the testing that I have done I am pretty certain it is the wire harness for the MDS which I plan on changing in both vehicles. It's a small wire harness that runs under the intake manifold.

I haven't bothered with it because the truck runs perfectly fine with the oil sensor unplugged I just make sure that i check my oil levels often.

 

[SteveSchwab]

Do you know if you unplugged the oil pressure sensor, or was it the oil temperature sensor?

Do you get a check engine light with the sensor unplugged? If so, what code?

 

[blazz81]

 

[blazz81]

I reset the computer the MDS code hasn’t popped back up yet in the above picture.

 

[blazz81]

Today i started working on the 2nd durango(blue) i found out if i unplug the MDS jumper wire i can hear the MSD solenoid click and durango runs good and sure enough when I plug it back in it start running on 7 cylinders again. So it seems to be getting power from somewhere all the time.. This is not the same with the original durango(gray) from my original post. This can't be a short in the jumper wire because I'm disconnecting it.
It must be coming from the main harness somewhere seems like I'm going to be doing a lot of wire checking possibly a computer issue with durango(blue)

Some helpful info..
A bad MDS jumper wire. I found this not my wire!