Note on Intermittents
WARNING: This page is about a different car, the 1990 Cadillac Fleetwood and 1990 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
Manipulate circuit No. 410 wiring, coolant sensor and ECM connectors while observing ECM parameter P.0.4. If failure is induced, coolant temperature will jump from its normal value to shorted readings of 288°F (142°C) or greater. Remove and replace both coolant sensor and ECM connectors and ensure they are latched before replacing components.