482 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
IDM PWR Pi n- Po in t Diagnostic s
Figure 474 IDM PWR circuit diagram
The IDM PWR circuit requires the use of vehicle circuit diagrams. See truck Chassis Electrical Circuit
Diagram Manual for circuit numbers, connector and fuse locations.
CAUTION: To avoid engine damage, turn the ignition switch to OFF before removing main power relay or any
IDM connector supplying power to the IDM. Failure to turn the ignition switch to OFF will cause a voltage spike
and damage to electrical components.
Voltage C hecks at IDM Power Relay Socket – Key-On Engine-Off (Follow tests in order. Check with relay
breakout harness connected to relay and power distribution center and turn the ignition switch on. If all tests
are in sp ec, proceed to 1 2–pin voltage checks.)
Test Point
Spec Comment
86 to gnd 12 V ±1.5 V
Continuous voltage. If no voltage, check power circuits from battery or fuse.
If fuse is blown, check for short to ground. If fuse is good, check for open
between Pin 86 and B+. See truck Chassis Electrical Circuit Diagram Manual
for circuit numbers, connector and fuse locations.
30 to gnd 12 V ± 1.5 V
Continuous voltage. If no voltage, check power circuits from battery or fuse.
If fuse is blown, check for short to ground. If fuse is good, check for open
between Pin 30 and B+. See truck Chassis Electrical Circuit Diagram Manual
for circuit numbers, connector and fuse locations.
85 to gnd 0.06 V to 2 V
If > 2 V, check f or open circuit between IDM Pin X3-27 to Pin 85 on relay or
V
IGN
circuit – continue with 12–pin v oltage checks.
87 to gnd 12 V ±1.5 V
Continuous voltage. If previous test points are in spec and no voltage is
present, replace relay.
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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