Engine temp and ambient sensor issues

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Bandofmisfits

Junior Member
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Dec 14, 2021
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Location
ND
Ram Year
2018
Engine
6.4l Hemi
I've got a 2018 Ram 2500 with 6.4l hemi, it has 157,000 miles. The ambient temperature sensor is reading -40 so it's obviously bad (CEL indicates it's bad). When that happened the engine temp will get up to 185° and not move from there (not even by 1 degree). The heat coming from the vents is warm but not hot. I can hold the upper rad hose and the bottom is cold which tells me it is most likely reading somewhat correct for the coolant temp. I went ahead and replaced the thermostat and afterwards the check engine light went off and the ambient temp was reading 1° off actual outside temp, engine would get up to 224° and drop to 208°. About 2 hours after replacing the thermostat and it showing a fluctuating coolant temp with HOT air flowing out of the vents, the check engine light came on due to ambient temp sensor again, when this happened the coolant temp was and still is sitting at 185° with warm heat again...is this a coincidence to have both issues at the same time or is it related to the ambient sensor? I've ordered a new sensor and still waiting for the part but I'm wondering if anyone else has experienced this.
 
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Bandofmisfits

Junior Member
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Dec 14, 2021
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Location
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Ram Year
2018
Engine
6.4l Hemi
For anyone searching on Google with the same type off issue that I had. After replacing the Ambient Air Temperature Sensor and clearing the CEL the engine temp went back to fluctuating like it always has (prior to that it sat at 185°, wouldn't get warm) and there was hot air coming out of the vents. If your sensor goes out and your heat starts acting weird...that's why.
 

turkeybird56

Military Vet 1976-1996 Retired US Army
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Location
Central Texas
Ram Year
2019 Bighorn, 4 X 4, 3.21 rear, Bright Flame Red Pearl Coat, Mopar tonneau cover,Westin Bed rug
Engine
Hemi 5.7
For anyone searching on Google with the same type off issue that I had. After replacing the Ambient Air Temperature Sensor and clearing the CEL the engine temp went back to fluctuating like it always has (prior to that it sat at 185°, wouldn't get warm) and there was hot air coming out of the vents. If your sensor goes out and your heat starts acting weird...that's why.
Interesting, but SOMETIMES I think these Trucks are too smart for our own good.
 
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