So either my cooling system rocks out I have a bad sensor.
25 mile drive to work. 15 miles at around 55-60 and engine temp never rise over 175 F (speed and temp readings off ultraguage). About 40 degrees this morning. Guessing the ecu needs to see about 185-ish to start shifting/fuel mapping right. The dash gauge reads right in the middle.

 

Have you done work on your cooling system? How long have you owned the truck? Are you sure the previous owner didn't pull some shenanigans like removing the thermostat?

 

Haven't done anything to the coolant system except check it's level, freeze point, and appearance. All looks good.
I've had it since June '15 only really got it on the road last couple months.
PO didn't work on it. He took it to an European import shop in town. They did all the work. Haven't found any weirdness.
Upper hose gets hot enough that I don't want to hold onto it. I did replace the viscous clutch. Didn't think to bring my infrared temp gauge this morning. I'll zap it when I get home.

 

From what I have read, ecu starts closed loop at 160 degrees.

 

Check coolant level in morning when cold prior to drive to ensure low temp not result of low level and air in system. More than once folks have noticed odd low temps and discovered low coolant to be cause of low indication. If already checked stone cold good for you as well as thinking of checking with IR. Suggest IR check done at sensor versus elsewhere. Did myself recently with IR and all over map except at base of senor/manifold.
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My truck doesn't get over 180F unless its above 40F on my drive into work. It struggles to break 170F when its real cold in the morning. Everything in my system is A-OK, so I'd say your conditions are normal. You need to get above 160-165 and after that you're in the clear with fuel burn and emissions and whatever.

 

OK, so the 55-60 is MPH not degrees F and the 40 is ambient?

Remember monitoring temp/loop on my ScanGaugeII a couple of times and believe only needs to see about 140 F for fuel schedule.

Recommend those questioning their operating temp readings high or low to check ECT sensor at manifold compared to a IR thermometer aimed at it. My D2 sensor output is about 5 F higher than IR reading and fine with me since actual temps a bit lower. $20 or less temp senors work good/last a long time but not known for exacting accuracy and probably should be checked occasionally as they are a component of a vital indication/warning system.
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Yes, 55-60 mph and 40 deg. ambient.

Drove 25 miles tonight. About 50-ish ambient. Same temp readings (164-174 F) on ultraguage. IR at sensor/housing was 190 degrees at idle at end of trip. Ordered a temp sensor a few days ago for ghits and siggles.

Bonus: Discovered my coil pack is grounded good. Saw sparks jumping around. 😒😒:-/

 

If anyone can help out I have developed this same issue recently. Temps were consistently 188-199. Not temps fluctuate in the 170s... Maybe a stuck thermostat which I haven't checked but the thermostat is only a couple months old and had been functional. I noticed that the temp went down to 150 or so and then right back up to 170 at one point which leads me to think its an electrical issue.

have replaced the coolant temp sensor (2 wire that feeds the ECU) and no difference. Tested connector and its getting 5V which I think is the correct amount.

Maybe my truck is running so ****ty due to my fuel pump that it actually can't generate enough heat?

but saw this thread and thought I would see if anyone had any leads.

 

Wanted to bump this and see if anyone has any thoughts.

Pretty sure I have a 190F thermostat in there (stock) and my truck is running 175-179 all of a sudden. Fixed my fuel pump and truck is running better but still colder than ever. And I don't understand how it can run below thermostat temp...

Sensor shows 222 ohm after a long drive with gauge reading in the 170s. Bad sensor/electrical issue or truck just running colder?

I did replace my fan clutch recently but subsequently the truck was still running in the 190s...

RAVE says "8K ohms at - 30°C to 90 ohms at 130°C, and 300 Ohms at 85°C" so my reading would suggest HIGHER than 85C or that I have a ****ty ohmmeter.