490 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
low side output supplies a return circuit to each injector
coil.
The injectors are under the valve covers. Each
injector has a close and open coil. The IDM
continuously monitors the amount of time (rising time)
taken by each coil to draw 20 A . The time is compared
to c alib rated v alues and the IDM determines if a
circuit or injector fault exists. Each injector has 6
failure modes and 3 DTCs. A failure can occur on the
open or close coil circuit.
Whenashorttogroundconditionisdetectedonan
injector (low or high side), the IDM discontinues power
to the shorted injector and operates the engine on the
remainin g cy linders.
INJ Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamp. The
last digit in the injector DTC corresponds to the
cylinder where a fault has been detected.
DTC 421-426
High side to low side open
• DTC 421–426 is set by the ECM when the rising
timeistoolongfortheopenorclosecoil. DTC
421–426 usually indicates a harness or coil is
open.
• DTC 421–426 does not set the amber ENGINE
lamp.
DTC 431-436
High side shorted to low side
• DTC 431–436 is set by the ECM when the rising
time to 20 A is short, but not zero for the open
or close coil. DTC 431–436 usually indicates an
internally shorted coil.
• DTC 431–436 does not set the amber ENGINE
lamp.
DTC 451-456
High side short to ground or V
BAT
• DTC 451–456 is set by the ECM when the rising
time to 20 A is zero for the open or close coil. DTC
451–458 usually indicates the harness or coil is
shortedtoground.
• DTC 451–456 does not set the amber ENGINE
lamp.
Tools
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
• Digital Multimeter (DMM)
• Terminal Test Adapter Kit
INJ Pin-Point Diagnostics
WARNING: To avoid serious personal
injury or possible death, do not perform voltage
checks with the engine running. Injector soleno
id
operating voltage of 48 V DC @ 20 A is present on
injector circuits.
CAUTION: To avoid engine damage, turn the ignit
ion
switch to OFF before disconnecting the connec
tor or
relay for the IDM. Failure to turn the ignit
ion switch
to OFF will cause a voltage spike and damag
eto
electrical components.
Before doing injector diagnostic testin
g:
1. TurntheignitionswitchtoOFF.
2. Disconnect IDM connectors (X1 and X2).
All tests are checked at harness end. Pi
n numbers are
marked on all connector mating ends. A
fter checking
resistance through injector coils an
dresistanceto
chassis ground, if tests are within s
pecification and
DTC is a ctive, replace the injector
.
NOTE: Only diagnos e inje ctors w it
hactiveDTCs.
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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