Section 4
TM 9-2320-363-20-1
TROUBLESHOOTING CHARTS
D. CHART4. NO "CHECK ENGINE'' LIGHT DURING BULB CHECK OR CANNOT CLEAR 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.
C4-1 Try to Force CEL On
l Turn ignition off.
l Disconnect the vehicle harness
connector at the ECM.
l install a jumper wire between socket
B1 on the vehicle harness
connector and a good ground.
l Turn the ignition on (engine not
running).
l Note the CEL status.
C4-2 Check for Ignition
l Remove jumper wire.
l Read voltage on vehicle harness
connector. socket B3 (red lead)
to a good ground (black lead)
with the Ignition on and engine
off.
C4-3 CEL Driver Line and
Bulb Check
l Turn ignition off.
l Remove CEL bulb and check
whether it's burned out or
otherwise damaged
Go to C4-2.
GO to C4-4.
The 5 Amp, ignition fuse is
blown and/or wires #2 or ##3 are
open or shorted to ground,
and/or the ignition line (ckt
#439) is shorted to ground or is
not wired to switch ignition
source (See note below).
Repair problem, page 3-2.
Then go to C4-30.
Go to C4-3
CEL Driver line (ckt #419) or ground
line (ckt #150) is open. Contact
Direct Support. Then go to C4-30.
Replace bulb. Then go to C4-30.
l NOTE: Historical codes will not clear and engine hours/fuel consumption values will not update if main ECM power (circuits
#240 and #241 ) IS switched off with ignition.
3-163
