Hi
My 91 intercooled truck grid heaters are not cycling . I had a electrical surge go through the truck a while back and I replace the PCM with one out of a 92 or 93. Grid heaters worked before the surge but not sence

When I turn the key forward the wait to start light does not come on
Once the key is in the starting position or the truck is running the wait to start light is on but the heaters never cycle even after the truck is running
I talked to the guy who I got the PCM from and he said he didn't believe the grid heaters worked in the truck it came out of either

My question is do I buy a new PCM $215 or is there something else that would cause this symptom .

I don't get why the wait to start light come on after the key is all the way forward but not be for that position

 

The PCM is different for a 91.5 to 92-93 . I believe you need a 91.5 PCM to make it work right .

 

Really? that's wild . I thought all that stuff would be the same 91.5-93

 

no 91.5 is the Wild Child it has aux voltage reg where as the other 2 yr's have it built in to the PCM. I personally Hate 91.5 truck's because None of the wiring interchanges with 92-93 Tehy are the Messy r of the truck's .

 

Thanks for the help. My problem now is that I can't find a parts store that can get one including the dealer . does anyone know where I can get one . or if I can find my original ecm where I could get it repaired ?

 

There are a lot PCM rebuilders that will rebuild your PCM if you send it to them, I have used "Auto ECM Electronics", you can google them. I am not affiliated with them in any way but they repaired mine in less than 2 weeks including shipping time both ways any they give you a lifetime warranty.

 

If nothing else and the Grid Heater's are the Only thing not working .Just Put them on a Switch .