2018 6.4l 2500 P0174 P0171 and P0128

[Gr8g]

Hello, new to this forum and Ram family. I recently purchased a 2018 Ram 2500 with a 6.4L and 105k Km. Since purchasing it has been in shop. Shortly after the purchase the check engine light came on. I took it right back to dealership and they looked it over. They had the truck for a week trying to resolve the issue. I was told the truck was fixed. I was told that fuel pressure was to low 10psi. So, they ended up replacing the fuel pump and pressure went up to 50psi which I was told was normal. The fault codes were cleared and the truck was driven by mechanic and salesman for awhile. It was declared fixed. I went to pickup the truck and when I turned it on the CEL came back on. I took the truck home for the night. While at home I put my code reader on it and got a P0171 P0174 and P0128. Can the P0128 be related in any way to the lean codes? The P0128 is a thermostat sanity check I believe so don't see how they can be related.

 

[GTyankee]

this is the best website to get a very good trouble shooting guide.
Read the complete page, for each trouble code

P0128 Coolant Temperature Below Thermostat Regulating Temperature

How to quickly diagnose, repair, and info on symptoms and causes of a P0128 code which generally indicates a failed thermostat.

www.obd-codes.com

OBD-II DTC: P0171 System Too Lean (Bank 1)

OBD-II Trouble Code: P0174 System Too Lean (Bank 2)

 

[Wadejesu]

If someone stuck a low temp stat in there like a 160 or 180 you will get those codes during warm up

 

[Gr8g]

Thank you for the info. For the lean codes could this be due to the MAF or MAP? My understanding is the Hemi uses a MAP but, when I look on the Mopar site I see a part number for both. MAF - 68144197AA and for MAP - 68371847AB

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[Gr8g]

I just heard back from shop they found 3 fuel injectors that were bad. They replaced those 3 and say the truck is running alot better. The check engine light is still on apparently but, was told this was due to the fact new injectors were installed so, a firmware update is required. This does not make sense to me. Why would changing out fuel injectors require a firmware update? Is it okay to just replace 3 out of 8 injectors? I would think you'd do them all at once. The cost of this work is all on the dealership. Are they trying to save money and will I have issues with the others in the near future if the others were replaced?

 

[2003F350]

It is pretty common on a gas engine to just replace bad injectors, not an entire set. They're completely electrically controlled so it's not like the old oil-fired ones in older diesels - the wear rates on gas injectors aren't always the same.

If the CEL is still on then the truck isn't fixed yet - they need to figure out why the codes keep tripping.

It's entirely possible that the truck does need a firmware update - if someone never did it then there could be some updates that need to be installed. I wouldn't think it would cause any CEL though.

Agree with the above, if someone put in a lower temp thermostat then you'll get funny codes, the only way to tell for sure is to see what operating temp it gets up to and stays consistent at while driving. I want to say it was around 200 for my '17 6.4.