jeepmojo

where the sensor is located on the 3.6 2012 ive replaced the thermostat 3 times
and every season the first frost we get it trips the check engine light . po128 codes. The thermostats always seem to be fine and operate properly along with heat in the cab
it was told to me it is most likely the sensor that is tripping the check engine light
but i need to find it on the engine block . I cant seem to locate it , A picture would be great ! makes no sense to keep replacing thermostats that are working if its just the sensor
thank you

karls10jk

Our own Ronjenx posted this picture and it's the first one to pop up on Google.

https://www.jk-forum.com/forums/jk-e...sensor-178989/

^^ for the 3.8 and you've got the 3.6, disregard please.

14Sport

This may help. It looks like you have to pull the left side inner fender liner to get to it on the 3.6.

ronjenx

Are other codes being set? (Checked with a code reader, not the self-read feature.)

jeepmojo

it was done at orileys parts. but last few times at dealer and they keep replacing tt at the cost of 210.00 not wanting to play the game anymore

jeepmojo

and draining system down ? that seems ridiculous just to screw a new sensor in place ! i can imagine how much the dealer would get to do this ?????
im trying to figure why the check engine light would trip every season on first cold day of the year. these thermostats cant be all be going bad . and vehicle appears to run fine and no sign of overheating, plenty of heat in the cab as well. even on long ride
is there any other recommendation out there on how to go about this . should i clear the code? see if it stays off . seeing the vehicle is running properly?
i cant keep paying them 210 .00 every time it throws a engine light to replace thermostats . never had a bad thermostat every year on the first cold day in other vehicles any suggestions would be appreciated
ps its fresh new coolant in there too.

14Sport

If it was me I would clear the code and see if it comes back. If not, you got another year. If so, replace the sensor.

ronjenx

Perhaps this information will help you understand what the computer is looking for:

P0128-THERMOSTAT RATIONALITY

Theory of Operation


The PCM predicts what the engine coolant temperature should be, based on the engine coolant temperature at start-up, ambient temperature and how the vehicle is subsequently driven. The predicted engine coolant temperature is compared to the Engine Coolant Temperature Sensor reading. The error between the two is calculated and integrated with respect to time. When the Thermostat diagnostic runs, the integrated error is compared to a calibrated threshold and pass/fail is determined. Separate pass and fail thresholds are used in order to improve accuracy of the diagnostic.

• When Monitored: With the engine running, ambient temperature between -8° C (17.6° F) and 50° C (122° F), start up coolant temperature less than 50° C (122° F), and average vehicle speed greater than 16 kph (10 mph) until coolant temperature reaches 85° C (185° F).
• Set Condition: The PCM detects that the actual engine coolant temperature falls too far below the predicted engine coolant temperature and the predicted coolant temperature reaches the predicted target value before the actual coolant temperature reaches the actual coolant temperature target value. Two trip fault. Three good trips to turn off the MIL.

[TABLE]
[TR]
[TD="bgcolor: white"]Possible Causes
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]LOW COOLANT LEVEL
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]THERMOSTAT OPERATION
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]SIGNAL CIRCUIT SHORTED TO VOLTAGE
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]TEMPERATURE SENSOR
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]SIGNAL CIRCUIT OPEN
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]SENSOR GROUND CIRCUIT OPEN
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]SIGNAL CIRCUIT SHORTED TO GROUND
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]SIGNAL CIRCUIT SHORTED TO THE (K900), (G931) SENSOR GROUND CIRCUIT
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]OTHER POSSIBLE CAUSES
[/TD]
[/TR]
[TR]
[TD="bgcolor: white"]POWERTRAIN CONTROL MODULE (PCM)
[/TD]
[/TR]
[/TABLE]

NOTE: If any ECT, AAT, CMP or CKP sensor DTCs have set along with P0128, diagnose them before continuing.



NOTE: Make sure that the Pinion Factor has been programmed correctly into the PCM.



NOTE: Diagnose any CAN - C Communication DTCs before continuing.


NOTE: If an Engine Coolant Temperature (ECT) DTC is set along with this code, diagnose the ECT DTC first.



NOTE: Inspect the ECT terminals and related PCM terminals. Make sure the terminals are free from corrosion and damage.



NOTE: The best way to diagnose this DTC is to allow the vehicle to sit overnight outside in order to have a totally cold soaked engine.



NOTE: Extremely cold outside ambient temperatures may have caused this DTC to set.



WARNING: Never open the cooling system when the engine is hot. The system is under pressure. Failure to follow these instructions can result in personal injury including extreme burns, scalding, or death. Allow the engine to cool before opening the cooling system.

jeepmojo

it gets pretty high tech for me to really understand but i get some of it ,what do they mean three good trips to turn off mil ? ill have orilelys clear the code po128
i will make sure there were no other additional trips with that code but from what i saw was only po128 . see what happens . i think its maybe i didnt allow it to warm up long enough before starting to move after it sat in real cold weather each time it trips the engine light it appears the same type situation being very cold and parked on a incline of some type all 3 times . oddly enough i feel they are not related to a bad thermostat however dealer keeps replacing the tt at a cost of 200+
but thank you for the posts and replys all those who did !
helpful i hope it clears and stays off if so ill allow it to warm up longer before driving it on cold days like it or not . my jeep stays in high idle for a long time longer than most it seems . it can take litterly 10 min before it idles down even in warm weather it has to be warmed up before it idles down lol seems stupid 80 degrees out and im waiting for my jeep to warm up .

jeepmojo

so far so good , not saying it wont go on again in frigid weather but it did not re appear all day . knock on wood at least i know what to expect
there were no other codes along with that as mentioned . see how things go now.