I have a 1996 SS convertible that the fans will not kick on. They do come on low when you turn the A/C on. They come on high when you unplug the temp sensor. but they wont operate when the engine comes to temp with the sensor pluged in. I have replaced the waterpump, temp sensor and Relays. could there be something wrong in the PCM

 

How hot does it get? What temp is "comes to temp"?

The stock programming is low speed fans at 226*F, high speed fans at 235*F.

 

It overheats it passes 240 gauge maxed out fans don't come on

 

Check the coolant temp sensor wiring for the one in the water pump housing. Check the accuracy of the sensor in the driver side head for the gauge:

4th Gen LT1 F-body Tech Articles

If you have access to a scanner, see what reading the PCM is getting, compared to the gauge reading.

 

One more thing to add. There is a plastic shield that is about 8 inches behind your front bumper. Its a air dam, ment to force air through your radiator at a certain speed.be sure you have this or you will overheat at higher speeds