Diagnostic aids – JLG 450A_AJ Series II Service Manual User Manual
Page 263
SECTION 3 - CHASSIS & TURNTABLE
3121180
– JLG Lift –
3-213
DTC 9999- Throttle Actuator Failsafe Spring
Failure
• Throttle Actuator
• Check Condition- Key Off, Engine Stopped
• Fault Condition- When key is off (or actuator is unpow-
ered), the ECM is expecting failsafe spring in actuator
to return throttle position to near 0%. If throttle does not
reach this position when actuator is powered, a fault is
generated.
• Corrective Action(s)- Illuminate MIL, sound audible
warning or illuminate secondary warning lamp. Govern
engine speed to a forced idle speed.
• Non-emissions related fault
Throttle actuator has a return spring that causes throttle to
move to a near 0% position when powered off. This
causes engine shutdown following a key off. If ECM
detects throttle position to be above x volts when key is off
(as determined by diagnostic calibration), it will power up
the actuator and attempt to drive it to a zero position. This
should ensure engine is stopped.
Fault sets if throttle does not return to a near 0% position
with key OFF.
Diagnostic Aids
• Disconnect throttle actuator from wire harness.
Remove throttle actuator from engine and manually
move it. Verify internal spring forces throttle back to
near 0% position.
• Inspect throttle arm or fuel rack on fuel pump. Verify it
is not stuck.
E
le
c
tro
n
ic
T
h
ro
ttle
A
c
tu
a
to
r w
/Se
ria
l
P
o
s
itio
n
F
e
e
db
a
c
k
2
1
6
1
3
1
2
1
5
V
_e
x
t
V
s
=
+
5
V
DC
5
V
_
rtn
T
P
S
1
T
P
S
S
ER
+
+
-M
o
to
r
D
B
W-
D
B
W+
E
C
M
H
-B
rid
g
e
1
9
T
P
S
S
ER
-
S
e
ria
l
x
m
itte
r
Electronic Throttle
Actuator w/Serial
Position Feedback
2
16
13
12
1
5V_ext
Vs=+5 VDC
5V_rtn
TPS1
TPS SER +
+
-
Motor
DBW-
DBW+
ECM
H-Bridge
19
TPS SER -
Serial
xmitter