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i was going to say horn but i figured he would know if his horn was hooked up
 

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If it just has the wimpy work truck horn, then that is the hook up for the other horn. I did that upgrade on my last truck.
 

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Unplug it and see if the reading on the mirror changes to 'OC' (open circuit).
 

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haha, this is great! I literally just took a pick last night of this and was going to ask the same exacth thing. Now that I know thats a temp sensor I can get the mirror wth the temp and direction in it and know it will work.

pic i took.
DSC01553.gif
 

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02GMCtruck
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There are two temperature sensors on many of the trucks, one for the mirror temperature reading and the other IIRC is for the ECM. If you add a mirror you should probably add an independant sensor for it as well. :D
 

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Not doubting you Dave.....never heard of the PCM having a seperate 'ambient' air temp sensor.
PCM uses the temp sensor near the thermostat housing and the IAT sensor in the air intake (or built into the MAF in later trucks).
 

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Lifted 2wd club
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Word. This temp sensor should be completely isolated from the PCM. It runs thru the fusebox then up the a-pillar to the mirror.
 

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I think it strange that the sensor would be there when the mirror isn't a temp mirror.
For the original poster....unplug it, look at the mirror and put an end to the debate.
 

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02GMCtruck
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That is interesting that GM would put the sensor in without a mirror. My 02 didn't have a comp/temp mirror or the sensor for it.

Also, Howard, I do know that the duramax trucks have two sensors for sure, one for the mirror and one for the PCM to control the elevated idle dependant on temperature. It seems logical that the gas motors wouldn't have two sensors since they dont' have this option, but it also seems weird for GM to install the sensor without the mirror......
 
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