7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS 399
Fan Clutch Circuit Operation
Figure 434 Fan clutch circuit diagram
The presence of elec tric current locks the fan clutch
into place and allows fan activ ation and cooling.
When the fan needs to be activated, the ground is
removed from ECM Pin X4–14. The coil side of the fan
relay is deenergized causing the switch side to close,
then sends 12 V from Pin 87A to the fan clutch. The
fan c lutch locks the fan in place w hen p ower is present
at Pin 87A.
When fan needs to be deactivated, Pin X4–14 is
grounded from the ECM. The coil side of the fan relay
is energized, causing the switch side to open, and
removes power from Pin 87A to the fan clutch. The
fan clutch unlocks the fan when the power is removed
from Pin 87A.
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. T he 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.
DTC 246
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
Tools
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
• Digital Multimeter (DMM)
• Relay Breakout Harness
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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