Code Po 128

[popeye47]

Hi Guys, So i got the po 128 code and decided to replace the thermostat and coolant in my 2018 ram 3500 limited, Afterwards the check engine light is still on?. Any ideas on how to proceed or do i have to just reset it, If so how do i do that.
Thanks

 

[nlambert182]

Typically if that's what was the culprit, it will reset itself after a few key cycles. You can also disconnect the battery for ~30 minutes or so. That may reset it.

However, it could also throw the code if the temp sensor or IAT sensor is bad. If it doesn't reset itself within probably 5-10 key cycles I'd start checking those. What's the temp gauge read when it's up to operating temps?

 

[popeye47]

I work nights so I haven't had a chance to drive it. But I warmed the truck up and got it to 189c .All I've done since is top up the coolant

 

[popeye47]

Sorry that's 89c 192f

 

[nlambert182]

The thermostat in a 2018 6.7 Cummins is a 190F. I think they switched from the 200F thermostat around 2017-2018.

I've seen my temps creep up to about 200 before it opens and cuts my temps back to ~ 188-194 depending on time of year. Right now with our temps in the low 30's in the mornings I don't usually see my temps make it much past 188. It shouldn't be causing a MIL light for low coolant temps around those temps IF the TSTAT is good.

There was a TSB out for P0128 but I can't recall the specifics.

 

[popeye47]

Thanks for the help, check engine light is now off but a new problem has arisen. After I put new coolant in I noticed I put a little to much in. So I syphoned some out, it's still a little high but now I'm getting white smoke occasionally from the engine compartment passenger side and exhaust smell in the cab. Can't see or feel any coolant leaks. I will syphon a little more out and get it right to the full mark. Any ideas please