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Q: ambient air temp sensor on 2004 Dodge Ram 1500

I installed fog lights on my truck, checked factory wireing comeing out at lights for power with ohm gauge found none but after that my engine light stays on and comes up with an ambient air temp. sensor code and temp gauge on overhead console reads -40c. how do I fix & where do I start looking, does this affect mpg?
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The air temperature switch that the vehicle's computer uses to calculate for fuel mixture is in the air cleaner housing. I see it having 4 wire on a diesel engine it and the wiring color is different for manual and automatic transmissions, If you tell me if the truck is manual or auto trans and 2WD or 4wd I can tell you the colors of the wires to look for but first see if it accidentally got disconnected. A gasoline engine has a two wire sensor in the intake duct or air filter housing the wires on this two wire sensor are dark blue/dark green and the other wire is dark blue/ light green.
The ambient air temperature switch for temperature control and outside temperature display is located between the drivers headlight area and radiator, the colors of the wires on the sensor are violet/light green and dark blue/dark green again ensure it is plugged in.
I also recently installed factory fog lights to my 2003 Ram 2500 2wd 5.7 Hemi. The factory wiring harness was already in place. It came as a kit which included the lights, the jumper harness that taps into the existing harness, and the new switch that replaced the existing headlight switch. Just like the original poster, I also have a check engine light and a reading from the ambient air temperature sensor of -40 degrees. To note, I did have to troubleshoot a bit on the fog lights. They didn't work once wired up and installed. I checked voltage at the point where the new harness plugs into the existing one and found nothing. Upon further investigation I found that my hot wire read proper voltage when checked between it and chassis ground. I then soldered a wire to the ground side of the harness and fastened it to chassis ground. the lights now work. Please help!
I know it has been over two years since you posted this, but I just had the EXACT same thing happen. Can you tell me if you ever found the solution to this?
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