P0128 code - thermostat?

[DaytonaRS7]

My lr4 seems to have it out for me lately.

Just got it up and running and I'm now getting a p0128 code.

The previous repair involved replacing the coolant temp sensor (due to physical damage) and draining/filling the coolant multiple times. Coolant system was filled using a vacuum tool.

I am consistently getting the p0128 code after a few miles of driving. Car seems to be getting up to temp in a normal amount of time. Just over 5 minutes of driving, when it's 20 degrees f ambient temp. I'm seeing no adverse problems due to the code.

Iid tool live readings has 2 values for coolant temp, once warm they hover around 90c and 70c consistently.

Coolant temp sensor replaced is the one in the coolant hose a few inches below the thermostat. Replaced it with eurospare brand sensor.

Before I throw parts at this, any insight? Can I save money and assume my thermostat is good since coolant temp readings seem appropriate?

 

[jlglr4]

Seems like that new temp sensor might be off. As I recall the temp sensor on the heater manifold at the back of the engine is the hot side sensor, and is where your temp gauge reads. Temp sensor below the t-stat is the cold side. It’s been a while since I checked my own temps, but I recall a larger temp spread between the two temp sensors. The other possibility is a bad t-stat, or bad wiring/connection to either t-stat or temp sensor.

You mentioned you replaced it due to physical damage - what happened to it?

 

[DaytonaRS7]

Seems like that new temp sensor might be off. As I recall the temp sensor on the heater manifold at the back of the engine is the hot side sensor, and is where your temp gauge reads. Temp sensor below the t-stat is the cold side. It’s been a while since I checked my own temps, but I recall a larger temp spread between the two temp sensors. The other possibility is a bad t-stat, or bad wiring/connection to either t-stat or temp sensor.

You mentioned you replaced it due to physical damage - what happened to it?

Bent broke, whipped around and hit the sensor, sensor broke.

Connector (vehicle side) seems fine, and since it is providing a reading, ill assume it is.

The information you're providing is the type I'm looking for. Can anyone confirm the coolant readings? And possible if they know which reading comes from which sensor.

I figure I've got those two options...replace thermostat or sensor. It would be a huge coincidence if the thermostat is bad. More likely the cheap eurospare sensor is ****.

 

[jlglr4]

I just checked an old log, and had 95F/219F at the two sensors, so 124 degree spread. Your spread (158F/194F) is only about 36 degrees. I’ll try to check it again later today with the engine hot and see what I find. However, I have the V6, and they do run at different temperatures compared to the V8. So if someone has temp values from a V8, it would be a better comparison.

 

[DaytonaRS7]

Ill wait for more people to chime in, but its probly safe to make the assumption that the spread should be similar, regardless of engine.

Maybe my situation is a bad thermostat, stuck open and the reading would on both sensors would be the same if it wasnt for the 20f ambient temp right now.