Section 4
TROUBLESHOOTING
TM 9-2320463-20-1
D. CHART5. “CHECK ENGINE” LIGHT ON AND CODE 25 ON DDR
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.
C5-1 Check for Short
(Ckt #451)
l Turn ignition on. observe ‘Check
Engine” light.
l Start engine and increase RPM
with throttle and observe “Check
Engine” light.
C5-2 Check for Short
(Ckt #419)
l Turn ignition off.
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
CS-3 Force CEL On
l Install a jumper wire between socket
B1 of the vehicle harness
connector and a good ground.
l Observe "Check Engine” light
RESULT
I
WHAT TO DO NEXT
Check for short to ground on
Diagnostic Request (Ckt #451).
Contact Direct Support.
Then go to C5-30.
Go to C5-2.
CEL Driver line (ckt #419) is
shorted to ground. Contact Direct
Support. Then go to C5-30.
Go to C5-3
Go to C5-4.
The ignition line (ckt #439) is not
correctly wired to the CEL bulb.
See if the bulb has been wired
into the ignition line (#439)
instead of the proper #419 wire
Correct problem. Then go to
C5-30.
3-169
