Service Manual Manual

SECTION 3 - 1CHASSIS & TURNTABLE
3-188 – JLG Lift – 3121171
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.
PINK/WHITE
4
3
5
1
2
TAN/ORANGE
GREEN/RED
PURPLE/BLUE
BLACK/GREEN