JLG 450A_AJ Series II Service Manual - Manual (Page 168)

SECTION 3 - CHASSIS & TURNTABLE
3-128 – JLG Lift – 3121290
DTC 336- Crank Signal Input Noise
• Crankshaft Position sensor.
• Check Condition- Key On, Engine On.
• Fault Condition- Electrical noise or irregular crank pattern
detected causing x number of crank resynchronization
events as defined in diagnostic calibration.
• Corrective Action(s)- Illuminate MIL and/or sound audible
warning or illuminate secondary warning lamp and disable
adaptive fueling correction for remainder of key-cycle.
• 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 deter-
mines crankshaft position (with respect to TDC cylinder #1
compression) and the rotational engine speed.
Determination of crankshaft position and speed is necessary
to properly activate ignition, fuel injection, and throttle gov-
erning systems for precise engine control.
The ECM must see a valid crankshaft position signal while run-
ning. If no signal is present, signal amplitude is too high (due
to improper air gap with respect to trigger wheel), or an irreg-
ular crank pattern is detected causing the ECM to resynchro-
nize x times for y ms or longer as defined in the diagnostic
calibration, this fault will set. Irregular crank patterns can be
detected by the ECM due to electrical noise, poor machining
of trigger wheel, or trigger wheel runout and/or gear lash.
Ensure crank circuit used with VR/magnetic pick-up sensors
are properly twisted.