sturmmorser2000

I just put a new ecm on my project 85 and used the original prom.I get a code 15 which is coolant sensor voltage high and I tried clearing it to no avail.The old coolant sensor was corroded an I replaced it.So i'm asking is it possible for the old prom to have the code 15 permanently burned into its memory and not clearing itself?

blackbear bob

Probably has a shorted wire. Codes are not "latch on" in early systems.
You will need to check the wiring carefully at the sensor. Most replacement sensors come with a new pigtail because the originals short out.

sturmmorser2000

the connector could very well be the problem.The wires don't come out very far when you unplug the connector and its gonna be a pain to strip and reconnect them to new connector with so little room to work.