My truck isn't running the heater grid when cold as it should. Wait to start is only lit for a second or so and goes out with water in fuel. That's based off the temp seen at the IAT sensor, right?Hopefully killed the sensor with diesel contamination and haven't given myself harness issues yet. Just replaced bad injection lines again... There's been lots of fuel loose under my hood

It has to be under 60F to work. If you got diesel fuel into that connector then it is likely shorting it out (making it think its hot), though it has a seal so it shouldn't get in there. Use a multimeter and check the resistance between the 2 sensor hole contacts in the IAT sensor. I am am not sure on specifics but I think it has to be at least 9000 ohms or greater to signal it is 60F or colder. As temps drop, resistance increases.. http://articles.mopar1973man.com/index.php?option=com_content&view=article&id=102:grid-heater&catid=34&Itemid=115

This is the 24V IAT sensor values which might just work for ya...[TABLE][TR][TD=width: 50%, bgcolor: #3870cc]Temperature[/TD][TD=width: 50%, bgcolor: #3870cc] Resistance[/TD][/TR][TR][TD=width: 50%] 13°F[/TD][TD=width: 50%] 56K ohms[/TD][/TR][TR][TD] 26°F[/TD][TD] 39K ohms[/TD][/TR][TR][TD=width: 50%] 87ºF[/TD][TD=width: 50%] 7.4K ohms[/TD][/TR][TR][TD=width: 50%] 91°F[/TD][TD=width: 50%] 6.8K ohms[/TD][/TR][TR][TD=width: 50%] 100°F[/TD][TD=width: 50%] 5.6k ohms[/TD][/TR][TR][TD=width: 50%] 107°F[/TD][TD=width: 50%] 4.7K ohms[/TD][/TR][TR][TD=width: 50%] 112°F[/TD][TD=width: 50%] 4.3K ohms[/TD][/TR][TR][TD=width: 50%] 119ºF[/TD][TD=width: 50%] 3.6K ohms[/TD][/TR][TR][TD=width: 50%] 123ºF[/TD][TD=width: 50%] 3.3K ohms[/TD][/TR][TR][TD=width: 50%] 127ºF[/TD][TD=width: 50%] 3.0K ohms[/TD][/TR][TR][TD=width: 50%] 132ºF[/TD][TD=width: 50%] 2.7k ohms[/TD][/TR][TR][TD] 143°F[/TD][TD] 2.2k ohms[/TD][/TR][TR][TD] 148°F[/TD][TD] 2.0k ohms[/TD][/TR][TR][TD] 163°F[/TD][TD] 1.5k ohms[/TD][/TR][TR][TD] 173°F[/TD][TD] 1.2k ohms[/TD][/TR][TR][TD] 184°F[/TD][TD] 1.0k ohms[/TD][/TR][/TABLE]