Notes On Intermittents
WARNING: This page is about a different car, the 1988 Cadillac Seville and 1988 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
Manipulate wiring on circuit Nos. 410PC and 476PC, coolant sensor, and ECM connector while observing ECM parameter ED04. If failure is induced, coolant temperature will jump from its normal value to the open reading of -35°C or less.
Disconnect and reconnect both the coolant sensor and ECM connectors, and ensure that they are properly latched. If wiring and connectors are okay, substitute and known good sensor and retest.
Review snapshot data parameters stored with this code to verify failure. If failure is verified, check and repair intermittent wiring connection or sensor.