Service Manual Manual

SECTION 3 - CHASSIS & TURNTABLE
3120788 – JLG Lift – 3-209
DTC 9999- Throttle Actuator Failsafe Spring
Failure
• Throttle Actuator
• Check Condition- Key Off, Engine Stopped
• Fault Condition- When the key is off (or the actuator is
unpowered), the ECM is expecting the failsafe spring in
the actuator to return the throttle position to near 0%. If
the throttle does not reach this position when the actu-
ator is powered, a fault is generated.
• Corrective Action(s)- Illuminate MIL, sound audible
warning or illuminate secondary warning lamp. Govern
the engine speed to a forced idle speed.
• Non-emissions related fault
The throttle actuator has a return spring that causes the
throttle to move to a near 0% position when powered off.
This causes the engine to shutdown following a key off. If
the ECM detects the throttle position to be above x volts
when the key is off (as determined by the diagnostic cali-
bration), it will power up the actuator and attempt to drive
it to a zero position. This should ensure that the engine is
stopped.
This fault will set if the throttle does not return to a near 0%
position with the key is off.
Diagnostic Aids
• Disconnect the throttle actuator from the wire harness.
Remove the throttle actuator from the engine and man-
ually move it. Verify that the internal spring forces the
throttle back to near 0% position.
• Inspect the throttle arm or fuel rack on the fuel pump.
Verify that it is not stuck.
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