Engine Cooling Fan: Operation: V8

Engine Control Module (ECM) uses primary and secondary electric cooling fan relays to control primary and secondary cooling fans. ECM uses input from A/C system, Engine Coolant Temperature (ECT) sensor and Vehicle Speed Sensor (VSS) to energize primary cooling fan. ECM will energize primary cooling fan when certain ECM Diagnostic Trouble Codes (DTC's) are stored, ECT sensor indicates greater than 226°F (108°) or A/C head pressure is greater than 248 psi (17.4 kg/cm² ).

When ECM energizes primary cooling fan, minimum run time is 50 seconds. If ECM energized primary cooling fan because of excessive engine coolant temperature, primary cooling fan will be turned off when engine coolant temperature drops approximately 5°F (15°C). If ECM energized primary cooling fan because of excessive A/C high side pressure, primary cooling fan will be turned off when A/C head pressure drops to 200 psi (14.1 kg/cm² ) or less.

ECM uses input from A/C system, Engine Coolant Temperature (ECT) sensor and Vehicle Speed Sensor (VSS) to energize secondary cooling fan. ECM will energize secondary cooling fan when certain ECM DTC's are stored, ECT sensor indicates greater than 235°F (113°C) or A/C head pressure is greater than 248 psi (17.4 kg/cm² ).

When ECM energizes secondary cooling fan, minimum run time is 30 seconds. If ECM energized secondary cooling fan because of excessive engine coolant temperature, secondary cooling fan will be turned off when engine coolant temperature drops approximately 5°F (15°C). If ECM energized secondary cooling fan because of excessive A/C head pressure, secondary cooling fan will be turned off when A/C head pressure drops to 208 psi (14.6 kg/cm² ) or less.