Check engine P-0128 cold weather

My ram promaster city has the Chrysler 2.4L tigershark engine. It’s still under warranty. This is my first cold winter with it, and the temperature here can range from 15 F in the early morning to 75 F in the afternoon. On a few occasions I have driven in the cold range and the CEL (Check Engine Lamp) has come on with code P-0128 which indicates “Coolant Thermostat (Coolant Temperature Below Regulating Temperature)”. I let it warm up before driving, and the temperature needle swings to normal after 5-6 minutes. So the dealer says to ignore it, this is a normal behavior they see all the time in winter. The lamp goes out if I start off in warmer weather for a few days, so it clears itself. So I wonder if this is safe to ignore, as the dealer recommends?

By warming up you are letting it run for awhile before you go anywhere , correct ? That is not what the manufactures recommend anymore . Start it let it idle for a few minutes while you clear windows then drive conservative for the first few minutes. If the dealer has put your complaint on file that will cover the warranty problem for waiting as the dealer has requested. If you don’t want to do that another dealer can verify or you can look in manual for higher contact with manufacture.

Below 50 F I do let it idle until the needle swings, 5-6 minutes, the idea being that cold air through the radiator and over the engine might extend the warm-up period. Otherwise, just a couple of minutes and then easy driving until the needle swings.

My owner’s manual has a break-in procedure, which was followed, but that was over a year ago. The manual does not specify anything about the startup sequence you are describing.

However it does state the following about the MIL : “The vehicle should be serviced if the light stays on through several driving cycles.”

In a way this answers the question, however my previous vehicle – 2005 Ford Five Hundred – never had this issue, but the computer might not have been testing for it either.

I’ll ask my mechanic next time I see him. I am not currently using him for this vehicle because it is still under warranty.

There was a bulletin issued in November for fault P0128 that involved a software update. Sometimes glitches occur when vehicles have not been tested in certain temperatures with particular operating conditions like excessive idling.

5-6 minute warm ups just waste gas and prolong cold running. All the bearings have oil in less than 30 seconds. The engine warms up fastest when being driven. The cold air through the radiator will not further cool the engine because the thermostat is closed until the engine reaches operating temperature.

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I’m not familiar w/that vehicle, but one idea is the radiator cooling fan is spinning when it shouldn’t. On most vehicles it’s only supposed to spin if the coolant is near or above the normal operating temperature. If the dash coolant temp gauge is below operating temperature, the cooling fan shouldn’t be engaged. Double check that. On my Corolla if I accidentally leave a connector disconnected the fan will spin all the time. It’s an electric motor fan. You may have a clutch activated fan powered by a belt from the drive train, but the idea is the same. A faulty thermostat is another possibility.

Do you think air blowing on the side of the engine will prevent it from reaching operating temperature? There is a lot of cold air passing though the front of the vehicle while traveling at 70 MPH.

Was it for one of the other Chrysler tigershark platforms? I don’t see anything in the NHTSA database for the 2016 ram pmc.

Your owner’s documents came with a protocol for moving the problem “up the ladder” in cases where the dealer response is unsatisfactory. I recommend using it and getting the manufacturer rep involved. If you try any repair yourself you may void the warranty for any related problems.

The vehicle should not be doing this.

Another example of waste would be damaging or destroying an engine by pushing it too hard at 15 F just to save an ounce of warm-up fuel.

Just checked – the fan is not spinning when cold. They have a thread over at the Chrysler 300c forum describing the algorithm based on the startup temperature and time. 8/10 times they discover a broken thermostat, at least on that vehicle. It will be nice to get the MIL taken care of so I don’t grow accustomed to seeing it.

BS. If this is normal, have them demonstrate it on another vehicle.

Unless you drive it like a lunatic or there is already something wrong, that won’t happen.

kid had same code in their saturn. low reading on temp gauge also. replaced thermo and no more code and temp gauge has risen. heat too.

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Double check w/dealership for tsb’s for that code per Nevada’s post above, and if that’s not the problem, I’d probably just replace the thermostat. Put the old and new thermostat in a pan of water on the stove and heat it up to 190 degrees, you may notice some difference. in the opening characteristics.