To add to the above, Code 15 is triggered (at least on the 94~95 LT1) when the ECM detects CTS at -40F or lower for 2 seconds. On this application, that means CTS circuit at 100700 ohms or more (open...

The temp gauge is driven by a different sensor than the one the ECM/PCM uses, so the dash gauge working doesn't mean the ECM is getting the proper temp. In fact, the Code 15 blatantly states that it...