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TM9-2320-360-20-3
Section 4
TROUBLESHOOTING CHARTS
D. CHART -9 - DIAGNOSTIC REQUEST SWITCH INOPERATIVE
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-III was started at step START-1 pg H-25 and you have now been referred here.
STEP/SEQUENCE
RESULT
WHAT TO DO NEXT
C 9-1
Check Diagnostic
Request Circuit
l Turn ignition on/engine
not running.
l Plug in DDR.
l Select SWITCH/LIGHT STATS
l Depress and hold diagnostic
request switch.
l Observe “Diagnostic Request
status on DDR.
C 9-2
Check SEL/CEL Bulb
l Turn ignition off.
l Remove CEL and CGL Bulb,
check to see if it is burned out
or damaged.
C 9-3
Check lgnition Line
l Turn ignition off.
l Disconnect vehicle harness
connector at ECM.
l Read voltage at cavity B3 (#439).
Display reads “ON”.
Go to C 9-2.
Display reads “OFF”.
Diagnostic request line (#528)
is open, or is not being grounded
when switch is depressed. Check
#528 wire and ground for
diagnostic request switch. Repair
problem then go to C9-30.
Display reads “N/A”.
Replace ECM (para 7-29.1).
Go to C 9-3.
Replace bulb(s) (para 7-40).
Then go to C9-30.
Less than
11.5v.
DDEC ignition circuit breaker
(CB11) is blown and/or ignition
line is open or shorted to ground.
Greater than 11.5V.
Ckt #419 or #509 is open.
Repair open and go to C9-30.
H-91
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