I got a 02 1500 with the 5.9 that the guy I bought it from put on a electric fan kit, it kept blowing relays so I pulled that all off and put on the factory fan, with the electric fan it was running half way, now it runs at a quarter way. A week later it throws the thermostat code, I replaced it, light goes off, 4 days later it’s back on same code so I decided to replace the coolant temp sensor, 3 days later code is back up again and I replaced the thermostat one more time and light is back on again. The heater is still blowing hot. Anyone got any suggestions on why it’s not getting up to temperature and throwing the same code.

 

What temp thermostat are you installing?

 

Replaced with a 195 first time, then when I had to replace it again I was told since it ain’t getting to temperature to put in a 160

 

160 will regulate the temperature around the 160 point. I'm surprised you're getting a code as I run a 160 as well to bring on the radiator earlier when I'm towing and I've never gotten a code.

 

Engine too cold too long.... I am surprised Prismatic has gotten away with it. The 2nd gen trucks weren't quite so picky as the newer stuff, but, even a 180 stat would set codes in those.

Put the stock temp stat back in. Reset the PCM, if the code comes back, time to start looking at coolant temp sensor.

 

Maybe there is some air trapped somewhere?

 

Wait, so it's already running cold, then you swap in a even colder thermostat? I don't follow the logic.

 

Same here. Putting a thermostat that is 30 degrees farenheit less before it opens just means that it would make the truck run cooler if I'm not mistaken.

 

Get a stock 203° thermostat, clear codes, give it a good warm up (like 10-15 min at least) and then drive it. For awhile. Lord knows how much condensation has been trapped in your oil driving it around cold like that. Need to get some heat in it.

 

In general, yes. But the "cooler" thermostat will also start to open up a little bit earlier, so that might make the PCM think it is broken as the "curve" (time vs. water temperature) is off/not met maybe?
And 160°F is really really "cold" in my opinion. I would be concerned that on average usage the oil doesn't get to its desired operating temperature.