Note On Intermittents
WARNING: This page is about a different car, the 1989 Cadillac Fleetwood and 1989 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
Manipulate circuits No. 410 and 476 wiring, the coolant sensor and ECM connector while observing ECM parameter P.0.4. If failure is induced, coolant temperature will jump from its normal value to open circuit reading. Disconnect and reconnect both the coolant sensor and ECM connectors and ensure they are latched before replacing components.