Radiator Fan Always On: P0128

My 2016 3.5L V6 recently started flashing the P0128 Code (Engine Coolant Temperature Below Thermostat Regulating Temperature). From my understanding, this code is displayed when the truck takes too long to get to operating temperature. I have had no issues with overheating, and the engine runs at temp once I have been driving for ~10min. Interestingly the radiator fan runs when the engine is cold (with the interior fan and AC off). My understanding, at least in older cars is that the fan will start running once the engine is hot. I have reset the OBDII and the code will return after a couple drives.

From my simple reasoning, the radiator fan being on when the engine is cold would result in the engine taking longer to reach temp, resulting in this code.

Is the radiator fan always on expected behavior in the 2016 Tacoma?

Are there any other troubleshooting steps I should take before taking it to the shop?

 

Belt driven fan, so it is on upon startup, but it should disengage within 10-20 seconds or so, on cold start anyways. Is your fan not disengaging right after startup?

 

Idk if it ever disengages, it just has more "slip" with the Clutch. OP I saw something today about the thermostat being stuck *open* and constantly bypassing coolant to the radiator. Could be your issue.

 

The fan is mechanical. Not sure if the thermal control is ECU based or still thermal spring based.

There can be multiple things create this condition, the most obvious being the tstat stuck in the open (or partially open) position. The coolant sensor itself can also be the problem.

 

It continues to run as long as the truck is on

 

Correct, they never fully stop, but obvious when it's fully engaged. I was an asking, because I was wondering if his wasn't disengaging/slipping and not letting the engine to warm up in a reasonable amount of time.

 

It spins, but that doesn't mean it's engaged and pulling max air flow.

https://help.summitracing.com/app/answers/detail/a_id/5272/~/how-does-a-fan-clutch-work?

 

See my reply to @Skydvrr , he's got a good point- they never fully stop, just slip/freewheel, or not fully engaged. A fully engaged clutch fan will have the fan spinning very fast and an obvious, fairly loud, whirling sound that changes with engine speed.

 

Has anyone else ran into this or found a solution? My 2020 just now started doing this. 14k miles and conveniently just out of warranty.

 

I recently had P0128 and replaced the thermostat this past weekend. The original t-stat has a plastic washer the gets dislodged and jammed sideways preventing the t-stat from fully closing resulting in the coolant never reaching operating temperature. Fairly easy fix. Took longer to bleed the system than to replace the t-stat. 2017 w/ 68k.

 

It doesn’t matter how much the fan is pushing air the thermostat should be able to regulate the engine temp. Replace the thermostat.

 

you by chance have a part number or link to the thermostat you bought? Thanks!

 

Dorman 902-5941.

 

This has been popping up on mine too. Guess I'll bite the bullet and replace that as well. I have enough money sunk into this damn thing I should have just bought a PRO LOL!

For anyone who's done it, I'm debating jacking my front end up and then replacing to to cut down on coolant loss, anyone do it that way or am I just being unnecessarily lazy? haha

 

My engine light went off on its own so apparently this issue temporarily resolved itself. Until next time no doubt…

I had planned to use a couple YouTube videos that go over changing the thermostat and doing a cooling system drain and fill for Tacoma. I planned to evacuate the coolant and then re-use it after replacing the thermostat. Haven’t done it yet though. Really don’t feel like doing this, lol!

 

Basically where I am too haha. It doesn’t seem difficult but the damn truck has 33k on it, there’s no way this sensor should be acting up already.

it’s getting to the point where if I didn’t have so much money wrapped up into it I’d just call it a day and get something else.