[shorod]

The DATC diagnostic code of 1966 is defined in the service manual as "Driver heater core discharge temperature sensor open circuit." The first step of troubleshooting for this code is to test the sensor resistance over temperatures. "Is the resistance within the specified values for these temperature ranges: 10-20°C (50-68°F) 37,000-58,000 ohms; 20-30°C (68-86°F) 24,000-37,000 ohms; 30-40°C (86-104°F) 16,000-24,000 ohms?"

It's been a few years since I was under the dash of an LS. I recall there being 2 or 3 temp sensors on the driver's side mounted in the center "stack" kind of in the area above the accelerator pedal. It might be easiest to pull the sensors and test them with a multimeter to the above values and see if any are bad or questionable. The sensors are interchangeable so you can move them around to see if the diagnostic code follows a particular sensor. If you don't find a bad sensor then carefully inspect the connections to make sure one is not damaged and not making a good connection to the sensor. After that you'll probably be stuck tracing wiring back to the DATC control head.

-Rod