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Robert R
Robert R, ASE Certified Master
Category: Dodge
Satisfied Customers: 3933
Experience:  Dodge Master Certified, Dodge Sprinter Certified
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My dodge hemi 5.7 liter mds engine seems to drop to 4

Customer Question

my dodge hemi 5.7 liter mds engine seems to drop to 4 cylinders much more often than usual
Submitted: 9 months ago.
Category: Dodge
Expert:  Robert R replied 9 months ago.

Hello, welcome and thanks for asking your question. My name is*****'m a Certified Auto Technician with 28+ years experience. I will do my best to assist you. please keep in mind that I may need to ask questions of you before I can answer. When you reply please feel free to add as much detailed information as possible pertaining to your concern.

Is the check engine light coming on while driving?

Under what conditions is it going to 4 cylinder mode?

How can you tell that it is going into 4 cylinder mode?

Does your vehicle have a factory or aftermarket exhaust system?

Keep me posted...

Thank you,

Robert

Customer: replied 9 months ago.
1 no 2when I don't need much power but it goes to 4 cyl mode way more often also if iam climbing a grade in 4 cyl mode and do not move throttle truck will keep slowing will not switch to 8 cyl mode unless I give it more throttle 3i can feel less power also I can hear it 4aftermarket dual exhaust
Customer: replied 9 months ago.
my truck mds system does not seem to be working properly
Expert:  Robert R replied 9 months ago.

Ok, the MDS is designed to go to 4 cylinder mode any time engine load and throttle position is below a certain threshold. Even if climbing a grade it may stay in 4 cyl mode unless you press the throttle a bit further. The fact that you have aftermarket exhaust makes it more detectable by the driver.

As long as the check engine light is not on, everything would be considered to be operating normally. If the PCM onboard diagnostics determine that the MDS is not activating or deactivating as requested a code would have been set in memory. There is NO way to change MDS operating characteristics unless there is a software flash update change provided by the manufacturer.

At this point I would recommend a scan to make sure there are no codes stored related to the MDS system. I recommend to have this done at a dealer in case there is a PCM software update. IF there are any updates, I HIGHLY recommend to have the dealer perform these updates an also have them reset the Adaptive Memory so that the PCM can properly "Relearn" all the engine operating parameters.

If after all the above is done drive the vehicle for a few days to see if things seem to improve, other than the suggestions above there is no other way to change the way the MDS system operates...

Keep me posted and let me know if you have any additional questions...

Thank you,

Robert