The presence of air pressure locks the fan clutch into place and allows fan activation and cooling.
When the fan needs to be activated, the ground is removed from ECM Pin X4–14. The air fan solenoid is deenergized and stops the flow of compressed air to the fan clutch. The fan clutch locks the fan when compressed air is not present.
When the fan needs to be deactivated, Pin X4–14 is grounded from the ECM. The air fan solenoid is energized and allows compressed air to flow to the fan clutch. The fan clutch unlocks the fan when compressed air is present.
Fault Detection / Management
An open or short to ground in the EFAN can be detected by the ECM during an on-demand engine standard test. The IAT and ECT are monitored continuously. If a DTC is detected in the IAT or ECT, the EFAN control is disabled and the engine fan is on all the time.
NOTE: Before diagnosing, check that ECM is programmed correctly. Verify vehicle / application
has an electronic fan.
EFAN Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the flashes from the amber and red ENGINE lamp.
Engine Fan – OCC self-test fault
• DTC 246 is set by the ECM only during the KOEO Standard Test. During this test the ECM performs an output circuit test that momentarily enables the EFAN solenoid and measures the voltage drop across the relay
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
• Digital Multimeter (DMM)