JLG 800S Service Manual - Manual (Page 164)

SECTION 3 - CHASSIS & TURNTABLE
3-118 – JLG Lift – 3121139
ECM and Sensors
CRANKSHAFT POSITION (CKP) SENSOR
The crankshaft position (CKP) sensor provides a signal
used by the engine control module (ECM) to calculate the
ignition sequence. The CKP sensor initiates the reference
pulses which the ECM uses to calculate RPM and crank-
shaft position.
CAMSHAFT POSITION (CMP) SENSOR AND
SIGNAL
The camshaft position (CMP) sensor sends a CMP signal
to the ECM. The ECM uses this signal as a "sync pulse" to
trigger the injectors in the proper sequence. The ECM
uses the CMP signal to indicate the position of the #1 pis-
ton during its power stroke. The CMP uses a Hall Effect
sensor to measure piston position. This allows the ECM to
calculate true sequential fuel injection (SFI) mode of oper-
ation. If the ECM detects an incorrect CMP signal while
the engine is running, DTC 53 will set. If the CMP signal is
lost while the engine is running, the fuel injection system
will shift to a calculated sequential fuel injection mode
based on the last fuel injection pulse, and the engine will
continue to nun. As long as the fault is present, the engine
can be restarted. It will run in the previously established
injection sequence.