JLG 510AJ Service Manual - Manual (Page 155)

SECTION 3 - CHASSIS AND TURNTABLE
3121181 – JLG Lift – 3-113
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 halleffect) 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 the rotational engine speed. Determina-
tion of the crankshaft position and speed is necessary to prop-
erly activate the ignition, fuel injection, and throttle governing
systems 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 the lack of crankshaft speed input
resulting in the inability to control ignition timing.
Diagnostic Aids
• Check that crankshaft position sensor is securely con-
nected to harness
• Check that crankshaft position sensor is securely installed
into engine block
• Check crankshaft position sensor circuit wiring for open cir-
cuit