Section 4
TM 9-2320-363-20-1
TROUBLESHOOTING CHARTS
D. CHART 6 . "CHECK ENGINE” LIGHT ALWAYS ON, NO DATA LINK AND WON'T FLASH CODES
NOTE — This chart is only to be used if:
1 ) All basic mechanical checks and physical inspections have been performed with no problem found, and
2) Diagnosis of DDEC-II was started at step Start-1 (page 3-121) and you have now been referred here.
C6-1 Check ECM Fuses
l Turn ignition off.
l Check both fuses or circuit breakers
to the ECM.
C6-2 Check for Open in DDL
Connector
l Check resistance between cavity
A of the DDL connector and a
known good ground.
l Disconnect the vehicle harness
connector at ECM.
l Check resistance between cavity
M of the DDL and cavity El of the
ECM 30 pin connector.
l Check resistance between cavity
J of the DDL connector and cavity
C2 of the ECM 30 pin connector.
l Check resistance between cavity
K of the DDL connector and
cavity Cl or the ECM 30 pin
connector.
C6-3 Check for Short
l Disconnect the vehicle harness
connector at the ECM.
l Turn ignition on (engine not running)
while at the same time observing
the “’Check Engine” light.
WHAT TO DO NEXT
Go to C6-2.
Replace blown fuse, page 4-
204. Then go to C6-30. (Note:
the fuse may blow again if an
intermittent short to ground
exists in either ckt #240 or
ckt #241).
Open in circuit. Contact Direct
Support Go to C6-30.
Go to C6-3
CEL Driver line (ckt #419) is
shorted to ground. Contact
Direct Support. Then go to C6-
30. The DDR system also needs
repair. Go to C7-4.
Go to C6-3.
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