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I was running ForScan to monitor my coolant temperature (automatic transmission if that matters) and found that the software would provide a coolant temperature reading only some of the time.
When it didn’t provide a reading, the software showed null.
Throughout that time, the temperature on the dashboard display showed middle of the range (though I’m actually not 100% sure if that shows engine oil temperature or coolant temperature).
I know that there is a coolant temperature sensor on top of the water pump. I also realize the system may have air in it (since I just changed the water pump) which may be causing the weird reading.
However, I would have thought the dash temperature display would also have gone to zero (unless it is in fact engine oil temperature).
With all that in mind, is there a second coolant temperature sensor somewhere in the truck?
For easier understanding of future readers, late model ZF6 manual transmission trucks are the only ones capable of reading coolant temperature from the factory.
Most people monitor EOT as there is about a 10° delta between EOT and ECT.
Don't believe a bit of what that dash gauge tells you either. It is programmed from factory to always read the same right up until it's damn near to late.