Oshkosh JLG 400S, Service And Maintenance Manual

Page: 218 / 462

SECTION 3 - CHASSIS & TURNTABLE
3-166 – JLG Lift – 3120895
DTC 336- Crank Signal Input Noise
• Crankshaft Position sensor
• Check Condition- Key On, Engine On
• Fault Condition- Electrical noise or irregular crank pat-
tern detected causing x number of crank resynchroni-
zation events as defined in the diagnostic calibration
• Corrective Action(s)- Illuminate MIL and/or sound audi-
ble 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 (vari-
able 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 com-
bination is used to determine crankshaft position (with
respect to TDC cylinder #1 compression) and the rota-
tional engine speed. Determination of the crankshaft posi-
tion and speed is necessary to properly activate the
ignition, fuel injection, and throttle governing systems for
precise engine control.
The ECM must see a valid crankshaft position signal while
running. If no signal is present, the signal amplitude is too
high (due to improper air gap with respect to trigger
wheel), or an irregular crank pattern is detected causing
the ECM to resynchronize 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 trig-
ger wheel runout and/or gear lash.
Ensure crank circuit used with VR/magnetic pick-up sen-
sors are properly twisted.