My pcm works normal when it warm but after it gets cold when you turn the key there is no wts light until you turn the motor on and there is no alt chargeing until the pcm warms up sometimes if i unplug the air temp sensor it makes the grids work before i start the truck, and if the grids work before i start the truck then i have no problems at all, so why does it work when warm but not cold.

 

Could be a connector moving with the temp and opening. More likely it's a fault in the PCM itself, like a cold solder joint, or a failing component.

 

Yeah sound's like a bad PCM

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