7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS 341
NOTE: Complete all pin-point diagnostics (ECM to valve cover gasket connector) bef
ore removing
valve cover for under-valve-cover diagnostics.
• Turn the ignition switch to OFF before disconnecting engine wiring harne
ss connectors from components.
•SeetruckChassis Electrical Circuit Diagram M anual fo r circuit num bers
, connector and fuse locations.
Actuator Control Voltage Check at ECM (Connect breakout box [X2 only] to ECM and engine harness.
Engine harness is not connected to v alve cover gasket. Connect 500 Ohm Resistor Harness to X2–18 and
ground. Turn the ignition switch to ON. Run Low and High Output State Test. For help, see “Diagnostic
Software Operation” in Section 3 (page 68) for procedure to run the Low and High Output State Tests.
Measure across X2–18 and ground.)
Test State/Point Setting/Spec Comment
KOEO DMM set to V - DC
X2-18tognd 0Vto0.25V
If > 0.25 V, disconnect engine harness from breakout
box harness and retest.
• If > 0.25 V, run the Low and High Output State
Tes t s.
• If < 0.25 V, diagnose engine wiring harness.
Check for short to V
REF
or B+.
Output State Test - Low DMM set to V - DC Toggling between the Low and High Output State
Tests can be done during this procedure.
X2-18tognd 0Vto0.25V
If > 0.25 V, disconnect engine harness from
breakout
box harness and retest.
• If < 0.25 V, diagnose engine wiring harnes
s.
Check for short to V
REF
or B+.
• If > 0.25 V with break out box connected
only to
ECM, replace ECM.
Output State Test - High DMM set to V - DC Toggling between the Low and High Output State
Tests can be done during this procedure.
X2-18tognd B+±0.5V
If < B+, disconnect engine harness from breakout box
harness and retest.
• If equal to B+, diagnose engine wiring harness.
Do Harness Resistance C hecks (page 342).
Check for short to ground or open circuit.
• If < B+ with breakout box connected only to ECM,
replace the ECM.
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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