Fan Clutch Circuit Operation - Navistar International DT 466 Diagnostic/Troubleshooting Manual

7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS

Fan Clutch Circuit Operation

Figure 434 Fan clutch circuit diagram
The presence of electric current 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 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 clutch locks the fan in place when power 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. 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.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
NOTE: Before diagnosing, check that ECM is
programmed correctly.
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
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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