Check engine light + no MDS

My truck threw a check engine light on my way in to work this morning. Didn't notice any difference in how the engine was running or the truck was driving, all fluid temps are normal. I've got a 6spd, 3.55s and 35's so MDS doesn't kick on unless I'm light on the skinny pedal, when I got off of the interstate I was driving conservatively and MDS did not kick on. I don't like the MDS but was thinking it may be a clue.

Any idea what may be going on? I'll try to get it to Autozone or something this weekend to read the code, just curious if this might be a common issue.

Do the 4th Gen trucks display codes on the screen like the 3rd Gens? If so, you cycle the key (if you have a key) from off to on, off to on, off to on and leave it.

EDIT: google searching seems it may not be possible on the 4th Gens.

How do you know MDS is not working? There are people that say they can tell by the sound of the exhaust, but in 3 years I have never been able to tell.

"ECO" shows up on the EVIC screen when MDS activates.

I went and had the code read and its P0441 whatever that'll do for me lol.

Phylodog said:

"ECO" shows up on the EVIC screen when MDS activates.

I went and had the code read and its P0441 whatever that'll do for me lol.

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P0441 OBD-II Trouble Code: Evaporative Emission Control System Incorrect Purge Flow

Usually a gas cap... But here is the list:

Bad gas cap
Faulty vacuum switch
Damage EVAP system line
Open or short in the wiring harness
Restriction in EVAP system
Evap leak
Purge valve

Hmm , subscribed for the info .

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Phylodog said:

"ECO" shows up on the EVIC screen when MDS activates.

I went and had the code read and its P0441 whatever that'll do for me lol.

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The trucks won't go into MDS or ECO mode if there's a check engine light on,they also won't remote start if you have a check engine light on.

This is my understanding--one of the Ram techs can correct me if I'm wrong----The "Eco" display and MDS do not necessarily work together. These two functions can work independently of each other. The "Eco" light indicates that you are driving "Economically". The MDS activates and drops cylinders, most often when highway driving with the cruise on, or when there is not "load" on the engine---at least in my truck. You can have both at the same time, but not necessarily. You can still have the "Eco" light illuminated but not have the MDS function operating.
Jay

R.L.K. said:

Hmm , subscribed for the info .

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Click to expand...

Same.


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P0441 OBD-II Trouble Code: Evaporative Emission Control System Incorrect Purge Flow
This indicates that a part of the EVAP control system is no longer functioning correctly. The EVAP system consists of many parts, including (but not limited to) the gas cap, fuel lines, carbon canister, purge valve, and other hoses.
The (EVAP) emission control system prevents the escape of fuel vapors from the fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.
This EVAP emission canister purge is controlled by a valve which allows engine vacuum to pull stored fuel vapors from fuel tank into the engine to be burned, rather than be vented to atmosphere.
A vacuum switch is used to detect when flow exists. If the PCM commands purge and sees that the switch is closed (indicating no detected purge flow) P0441 is set.
A code P0441 could mean one or more of the following has happened:
• Non-Vapor tight gas-cap <---number one cause, gas cap not tight or leaking vapor

• Bad vacuum switch
• Broken or damaged EVAP line or canister
• Open in PCM purge command circuit
• Open or short in Voltage feed circuit to Purge Solenoid
• Faulty purge solenoid
• Restriction in EVAP solenoid, line or canister
• Corrosion or resistance in purge connector
• Bad PCM <--highly unlikely given no discernible drop in performance

• Problem with fuel pump in gas tank

Common Chrysler fixes:
• Replace Gas Cap
• Replace Leak Detection Pump / LDP
• Repair damaged EVAP lines or canister
• Repair open or short in voltage feed circuit to Purge Solenoid
• Repair open in PCM purge command circuit
• Replace purge Solenoid
• Replace vacuum switch
• Repair restriction in Evap line or canister or solenoid
• Repair resistance in purge connector
• Replace PCM
• Replace Fuel Pump

Pull Ya said:

This is my understanding--one of the Ram techs can correct me if I'm wrong----The "Eco" display and MDS do not necessarily work together. These two functions can work independently of each other. The "Eco" light indicates that you are driving "Economically". The MDS activates and drops cylinders, most often when highway driving with the cruise on, or when there is not "load" on the engine---at least in my truck. You can have both at the same time, but not necessarily. You can still have the "Eco" light illuminated but not have the MDS function operating.
Jay

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Good explanation, as this is my understanding of the ECO light & MDS .

I also uderstand it as this , all of the parameters for ECO indication are required to be active for the full on MDS mode to be activated . I can't remember them all but I believe there are 13 diff parameters for full on activated MDS and there's only like 4 or 5 for the ECO indication to be displayed .

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I appreciate the useful info which has been posted. I've tightened the gas cap and for now I'm gonna hope that the CEL clears on its own.

ExpressRules said:

How do you know MDS is not working? There are people that say they can tell by the sound of the exhaust, but in 3 years I have never been able to tell.

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With a aftermarket muffler its super easy to hear it kick in, sounds like crap..lol

69GWC said:

With a aftermarket muffler its super easy to hear it kick in, sounds like crap..lol

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Not necessarily , I could hear the MDS kick in with my oem muffler more so than with my Carven Competitor Series

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Well you are young still, when your my age everything has to be loud before you can really hear it..lol

69GWC said:

Well you are young still, when your my age everything has to be loud before you can really hear it..lol

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LOL , I've been working on Turbine engines for 28 years and I'm on my 3rd set of hearing aids ...... the Carven Competitor Series is less noticeable than the OEM muffler imo

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But did you liston without your hearing aids ?? ..lol

I could use a hearing aid myself my wife gets tired of repeating everything after I say " What"...lol
skill saws and nail guns got my ears.

Phylodog said:

I appreciate the useful info which has been posted. I've tightened the gas cap and for now I'm gonna hope that the CEL clears on its own.

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Disconnect the battery so the code will be cleared. Otherwise it will take a long time for the correct monitors to run to clear the code on its own.

The gas cap likely isn't the issue, with failed gas caps you also get evap leak codes not evap purge performance. You might be lucky that was it, but in my 10 years of working on FCA vehicles I've never seen a leaky gas cap cause that code, it's actually not even listed as a possible cause in the service manual for that dtc. The most common things I've seen on the trucks have been the fuel tank pressure sensor, ESIM or the purge valve. Vast majority have been the fuel tank pressure sensor though.

I'd still just clear the code and see if it comes back first, it may take awhile to come back though. Evap **** can be very finicky.

Phylodog said:

"ECO" shows up on the EVIC screen when MDS activates.

I went and had the code read and its P0441 whatever that'll do for me lol.

Click to expand...

The ECO light just means you are driving in a thrifty way, but is not directly tied into MDS.