JLG 450A_AJ Series II Service Manual - Manual (Page 170)

SECTION 3 - CHASSIS & TURNTABLE
3-130 – JLG Lift – 3121290
DTC 337- Loss of Crank Input Signal
• Crankshaft Position sensor.
• Check Condition- Key On, Engine On.
• Fault Condition- Loss of crankshaft position signal while
valid camshaft position signals continue for x number of
cam pulses as defined in the diagnostic calibration.
• Corrective Action(s)- Illuminate MIL and/or sound audible
warning or illuminate secondary warning lamp.
• Emissions related fault.
The crankshaft position sensor is a magnetic sensor (variable
reluctant/magnetic pick-up or Hall effect) installed in the
engine block adjacent to a ¡§coded¡¨ trigger wheel located on
the crankshaft. The sensor-trigger wheel combination is used
to determine crankshaft position (with respect to TDC cylinder
#1 compression) and rotational engine speed. Determination
of the crankshaft position and speed is necessary to properly
activate the ignition, fuel injection, and throttle governing sys-
tems for precise engine control.
The ECM must see a valid crankshaft position signal while run-
ning. If no signal is present while x cam pulses continue, the
fault will set. The engine typically stalls or dies as a result of
this fault condition due to lack of crankshaft speed input,
resulting in loss of ignition timing control.
Diagnostic Aids
• Check crankshaft position sensor is securely connected to
harness.
• Check crankshaft position sensor is securely installed in
engine block.
• Check crankshaft position sensor circuit wiring for open cir-
cuit.