292 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
Harness Resistance Checks
Procedure
CAUTION: To avoid engine damage, turn the ignition
switch to OFF before disconnecting the connector or
relay for the ECM a nd ID M. Failure to turn the switch
to OFF will cause a voltage spike and damage to
electrical comp onents.
1. Check harness resistance if high resistance or an
open circuit is suspected.
2. Connect breakout harness to harness only.
3. Connect breakout box to the ECM end of the
harness only.
4. Measure resistance from breakout box pin to the
breakout harness pin. Circuit wires s hould have a
resistance of less than 5 ohms.
See Circuit D iag n os tics in this section for circu it
specifications.
Operational Voltage Checks
Operational voltages checks determine In-range
faults or intermitte nt connec tio ns.
To determine in-range faults and intermittent
connections, monitor a suspected circuit and recreate
conditions likely to cause the problem.
Monitor signal voltage with the EST using continuous
monitor session and initiating KOEO Continuous
Monitor Test. See Circuit Diagnostics in this section
for circuit specifications.
Use a DMM and breakout harness or a DMM and
breakout box. Se e Circuit Diagno stics in this s ec tio n
for circuit specifications.
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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