Section
4
TROUBLESHOOTING
CHARTS
D. CHART
21 THROTTLE
INHIBIT
ALWAYS ON
NOTE — This chart ISonly 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.
TM 9-2320-363-20-1
C21-1
Test Throttle
Inhibit
Feature
l Start and run engine.
l Plug DDR into the 12 pin DDL
connector and select Mode 29
(MISC SWITCHES) for display.
l Place vehicle in condition where
throttle inhibit is supposed
to
occur and observe DDR display
line labeled “POWER CTL SW’
(on coaches, this occurs when a
passenger door is open).
l Then place vehicle in condition
where throttle inhibit is not
supposed to occur and-observe
DDR display.
C21-2
Check
for Short
• Place vehicle in condition where
throttle inhibit will not occur and
observe DDR display (Mode 29).
l Turn ignition off.
l Disconnect the vehicle harness.
l Read resistance between pins H2
of the vehicle harness connector
and a good ground.
C21-3
Check
ECU
Connectors
l Turn ignition off (if still on).
l Disconnect the vehicle harness
connector at the ECM (if not
already disconnected).
l Check terminals at the vehicle
harness connector (both the ECM
and harness side) for damage;
bent, corroded,
and unseated
pins or sockets, especially
H2 of
the vehicle harness.
DDR display
reads “ON*’ always.
DDR display
reads “ON”, then “OFF”.
Less than or
equal to 5 ohms.
Greater than
5 ohms or open.
Terminals and
connectors
are okay.
Problem found
Connectors are okay.
WHAT TO DO NEXT
Go to C21-2.
Go to C21-4.
Either the Power Control Switch
is shorted or ckt#524
is shorted
to ground. Contact Direct
Support. Go to C21-30.
Go to C21-3.
Replace ECM, page 4-192.
Then go to C21-30.
Repair terminals/connectors,
page 3-2. Then go to C21-30.
3-201
