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TM 9-2320-364-20-2
2-1465
(1) Set multimeter select switch to
volts dc.
(2) Connect positive (+) multimeter
lead to TRANS relay R7, terminal 85.
(3) Connect negative (–) multimeter lead
to a known good ground.
(a) If 10 to 14 vdc are not present,
perform Step (8) below and
replace DDEC II ECM (Para 7-56)
or DDEC III ECM (Para 7-57).
(b) If 10 to 14 vdc are present,
perform Steps (4) through (8)
below.
(4) Start ENGINE (TM 9-2320-364-10).
(5) Shift transfer case to N (Neutral).
(6) Shift transmission to D (Drive).
(7) While assistant applies throttle control
for 10 seconds at 2000 rpm then
quickly releases throttle control,
observe multimeter.
(a) If 10 to 14 vdc are still present,
perform Step (8) below and
replace DDEC II ECM (Para 7-56)
or DDEC III ECM (Para 7-57).
(b) If 10 to 14 vdc momentarily drops
to zero (0) vdc, DDEC 508 circuit
is OK.
(8) Turn OFF ENGINE switch.
VOLTAGE TEST
Remove all jewelry such as rings, dog tags, bracelets, etc. If jewelry or tools contact positive electrical
circuits, a direct short may result. Damage to equipment, injury or death to personnel may occur.
Circuit breakers CB5, CB6, CB12, CB20, CB22, CB23 and relays R3, R13 - R19, R26, R28, R32, R33
are always electrically hot and can cause severe injury to personnel. Care must be exercised when
working under the electrical circuit board cover.
The DDEC 508 circuit grounds when the
engine drops to zero (0) throttle and
remains 150 rpm above a normal idle.
This will provide a ground for the TRANS
relay R7 coil.
Relay test must be performed with relay
partially removed.
On DDEC III trucks, wire 988 replaces
wire 508.
NOTE
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