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.

 

[Gr8g]

Well after taking truck to another mechanic and going through some of the paperwork from the previous shop we think we have figured out the lean codes. The previous shop before I owned the vehicle had done a lifter and cam shaft replacement. Looking at the part numbers of the Camshaft an aftermarket one was used. The Camshaft manufacture lists a camshaft with a part number SKMC1403 on their website. I called the manufacture to see if this was a replica of the Melling CM1403 which I was told it was. Looking at the Melling site the CM1403 is meant for the 5.7 Hemi with a MDS delete. My truck is a 6.4l hemi and the MDS has not been deleted. It has the MDS lifters in it. Talking to Melling they said that I would be experience lean codes if the CM1403 camshaft was installed on my 6.4L hemi. Skyward the manufacture of the SKMC1403 cam also said their catalog is wrong and they need to fix it. When I was looking at Rock Auto, Ebay, and other sites they all listed the SKMC1403 camshaft as an option for the 6.4L. Talking to Skyward I could here their jaw drop as I was asking the compatibility of their cam with the 6.4l and they said they don't make one for the 6.4L.

 

[2003F350]

Well after taking truck to another mechanic and going through some of the paperwork from the previous shop we think we have figured out the lean codes. The previous shop before I owned the vehicle had done a lifter and cam shaft replacement. Looking at the part numbers of the Camshaft an aftermarket one was used. The Camshaft manufacture lists a camshaft with a part number SKMC1403 on their website. I called the manufacture to see if this was a replica of the Melling CM1403 which I was told it was. Looking at the Melling site the CM1403 is meant for the 5.7 Hemi with a MDS delete. My truck is a 6.4l hemi and the MDS has not been deleted. It has the MDS lifters in it. Talking to Melling they said that I would be experience lean codes if the CM1403 camshaft was installed on my 6.4L hemi. Skyward the manufacture of the SKMC1403 cam also said their catalog is wrong and they need to fix it. When I was looking at Rock Auto, Ebay, and other sites they all listed the SKMC1403 camshaft as an option for the 6.4L. Talking to Skyward I could here their jaw drop as I was asking the compatibility of their cam with the 6.4l and they said they don't make one for the 6.4L.

Well then, there's your answer! And it does make sense, the cam profile for a 6.4 is different enough from a 5.7 (different displacements TYPICALLY mean different cam profiles but NOT ALWAYS, it also depends on valving and timing, something that's harder to alter on newer engines without a distributor) that it'll not open the valves far enough or long enough to pull enough air/fuel into the combustion chambers.

If you're still getting the thermostat code you may want to consider replacing it with a proper temperature one, but I'd say it's likely the least of your problems.

 

[Gr8g]

The thermostat code I think was from a rad with a hole in it. Had it over at Dodge and they found a hole in the rad. Which is funny cause I didn't see any rad fluid on the ground after parking it for after running it for awhile. The fluid was a bit low though. Had the rad replaced twice as the first replacement had a hole put in it during install. The mechanic installing it used the wrong mounting bolt which was too long. So, the bolt got sent right through it with an impact I'm guessing. Then they tried blaming it on a defective rad. You could clearly see where the bolt started making threads into the plastic housing of the new rad from. Any way they replaced it for the second time and the temp seems to maintain at 100C/212F and haven't seen the P0128 code since.

 

[Gr8g]

Just going to post this here in case it goes missing from Skyward's website in the near future for someone's reference.