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 circuits No. 410 and No. 976 (coolant temperature sensor and ECM connector), while observing ECM parameter ED04. If failure is induced, coolant temperature will jump from normal value to the open reading (-38°C or less). 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.