450 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
Harness Resistance Check – Relay to ECM Chassis G round (Turn the ignition switch t
o OFF. Disconnect
chassis connector 9260
1
. D isconnect c ontrol wiring from relay.)
Relay 1: A to Pin A (9260) > 1 kΩ If < 1 kΩ, check for short to ground within wiring harness.
Relay 1: B to Pin A (9260) < 5 Ω If > 5 Ω, check for open circuit. Specification is based
on 4300 chassis. For other applications, see Chassis
Electrical Circuit Diagram Manual for complete chassis
ground circuit information.
Relay 2: A to Pin A (9260) > 1 kΩ If < 1 kΩ, check for short to ground within wiring harness.
Relay 2: B to Pin A (9260) < 5 Ω If > 5 Ω, check for open circuit. Specification is based
on 4300 chassis. For other applications, see Chassis
Electrical Circuit Diagram Manual for complete chassis
ground circuit information.
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 Check – Relay to Chassis Ground (Turn the ig nition s witch to OFF. Disconnect
chassis connector 9260
1
. Disconnect negative battery cable. Disconnect control wiring from relay. U se
disconnected negative battery cable for ground test point.)
Relay 1: A to gnd cable
>1kΩ If < 1 kΩ, check for short to ground.
Relay 1: B to gnd cable
>1kΩ If < 1 kΩ, check for short to ground. S pecification is based
on 4300 chassis. For other applications, see Chassis
Electrical Circuit Diagram Manual for complete chassis
ground circuit information.
Relay 2: A to gnd cable
>1kΩ If < 1 kΩ, check for short to ground.
Relay 2: B to gnd cable
>1kΩ If < 1 kΩ, check for short to gro
und. Specification is based
on 4300 chassis. For o ther ap
plications, see Chassis
Electrical Circuit D ia gram
Manual for complete chassis
ground circuit informatio
n.
Harness Resistance Check – R el ay to ECM (Turn the ignition switch to OFF. Connect breakout box
[X1 only] to engine harness.)
Relay 1: Pin A to X1– 1 7
<5Ω If > 5 Ω, check for open in circuit.
Relay 2: Pin A to X1– 1 7
<5Ω If > 5 Ω, check for open i
n circuit.
Harness Resistance Check – R elay to 12–pin Connector (Turn the ignition switch to OFF. Connect
12–pin breakout harness to engine harness only.)
Relay 1: P in B to Pin 4 (12-pin) < 5 Ω If > 5 Ω, check for open in control wire.
Relay 2: Pin B to Pi
n 4 (12-pin)
<5Ω If > 5 Ω,checkforo
pen in control wire.
IAH Diagnostic Trouble Codes (DTCs)
DTC 251 = OCC self-test failed
1
Connector 9260 is a 2-wire connector usually located in the battery box. Pin A is the chassis ground connection for
the ECM and IDM. Refer to truck Chassis Electrical Circuit Diagram Manual for complete chassis side ECM and IDM
ground circui
t information.
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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