Note On Intermittents
WARNING: This page is about a different car, the 1990 Cadillac Seville and 1990 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
Manipulate wiring on circuit No. 410, coolant sensor, and ECM connector while observing ECM parameter ED04. If failure is induced, coolant temperature will jump from its normal value to the shorted reading of 148°C or greater. Disconnect and reconnect coolant sensor and ECM connectors, and ensure they properly latch. If wiring and connectors are okay, substitute a known good sensor and retest.