386 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
WARNING: To avoid serious personal injury, possible death, or damage to the engine or vehicle,
always disconnect main negative battery cable first. Always connect the main negative battery cable
last.
Harness Resistance Checks – Main Power Relay to Battery (Turn the ign
ition switch to OFF. Disconnect
negative battery cable. Disconnect harness from sensor. Inspect f
or bent pins or corrosion. Connect
relay breakout harness.)
30 (ECM relay) to B+ cable < 5 Ω If > 5 Ω, check connections for open between relay and positive
battery cable. Check fuses. See truck Chassis Electrical Circuit
Diagram Manual for relay and fuse locations.
86 (ECM relay) to B+ cable < 5 Ω If > 5 Ω, check connections for open between relay and positive
battery cable. Check fuse. See truck Chassis Electrical Circuit
Diagram Manual for relay and fuse locations.
Harness Resistance Checks – ECM to ECM Chassis Groun
d (Turn the ignition switch to OFF. Disconnect
chassis connector 9260
1
. Inspect for bent pin
s or corrosion. Connect breakout box [X3 and X4] to chassis
harness only.)
X3–6 to Pin A (9260) < 5 Ω If > 5 Ω, check connections to battery ground. See truck Chassis
Electrical Circuit Diagram Manual for relay and fuse locations.
X3–7 to Pin A (9260) < 5 Ω If > 5 Ω, check connections to battery ground. See truck Chassis
Electrical Circuit Diagram Manual for relay and fuse locations.
X3–3 to Pin A (9260) > 1 kΩ If < 1 kΩ,checkforshorttogroundwit
hin wiring harness.
X3–5 to Pin A (9260) > 1 kΩ If < 1 kΩ, check for short to g round within w iring harness.
X4–1 to Pin A (9260) > 1 kΩ If < 1 kΩ, check for short to g round within w iring harness.
X4–2 to Pin A (9260) > 1 kΩ If < 1 kΩ,checkforshorttogroundw
ithin wiring harness.
WARNING: To avoid serious pers
onal injury, possible death, or damage to the engine or vehicle,
always disconnect main negati
ve battery cable first. Always connect the main negative battery cable
last.
Harness Resistance Checks – ECM to Chassis Ground (Turn the ignition switch to OFF. Disconnect
chassis c onnector 9260
1
. Disconnect negative battery cable. Disconnect harness from sensor. Use
disconnected negative battery cable for ground test point.)
X3–6 to gnd cable
>500Ω If < 500 Ω, check for short to ground.
X3–7 to gnd cable
>500Ω If < 500 Ω, check for shor
t to ground.
X3–3 to gnd cable
>500Ω If < 500 Ω, check for short to ground.
X3–5 to gnd cable
>1kΩ If < 1 kΩ, check for short to ground.
X4–1 to gnd cable
>1kΩ If < 1 kΩ,checkforsh
ort to ground.
X4–2 to gnd cable
>1kΩ If < 1 kΩ, check for short to ground.
Harness Resistance Checks – ECM to Ignition Power Relay (Turn the ignition switch to OFF. Inspect for
bent pins or corrosion. Connect relay breakout harness and breakout b ox [X3 and X4] to chassis harness
only.)
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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