JLG 450A_AJ Series II Service Manual - Manual (Page 146)

SECTION 3 - CHASSIS & TURNTABLE
3-96 – JLG Lift – 3121180
3.13 FORD EFI ENGINE
Performing Diagnostics
1. Verify complaint and determine if it is a deviation
from normal operation.
2. Once complaint is verified, preliminary checks can
be done. Conduct a thorough visual inspection, be
alert for unusual sounds or odors, and gather diag-
nostic trouble code information.
3. Perform a system check to verify proper system
operation. Check for recent information updates.
4. If a diagnostic trouble code (DTC) is stored, contact
a JLG distributor to make an effective repair.
5. If no DTC is stored, select symptom from symptom
tables and follow diagnostic path or suggestions to
complete repair.
6. After repair has been made and validated for proper
operation, temporarily reinstall the old part to verify it
was the problem source.
If no matching symptom is available, analyze the com-
plaint and develop a plan for diagnostics using wiring dia-
grams, technical assistance, and repair history.
Intermittent conditions may be resolved by using a check
sheet to pinpoint the circuit or electrical system compo-
nent. Some diagnostic charts contain Diagnostic Aids
which give additional information about a system. Be sure
to use all of the information that is available to
you.
VISUAL/PHYSICAL ENGINE INSPECTION
CHECK
Perform a careful visual and physical engine inspection
before performing any diagnostic procedure. Perform all
necessary repairs before proceeding with additional diag-
nosis, this can often lead to repairing a problem without
performing unnecessary steps. Use the following guide-
lines when performing a visual/physical inspection check:
• Inspect engine for modifications or aftermarket equip-
ment that can contribute to the symptom. Verify electri-
cal and mechanical loads or accessory equipment is
“OFF” or disconnected before performing diagnosis.
• Inspect engine fluids for correct levels and leaks.
• Inspect vacuum hoses for damage, leaks, cracks,
kinks and improper routing, inspect intake manifold
sealing surface for a possible vacuum leak.
• Inspect PCV valve for proper installation and operation.
• Inspect all wires and harnesses for proper connections
and routing; bent or broken connector pins; burned,
chafed, or pinched wires; and corrosion. Verify harness
grounds are clean and tight.
• Inspect engine control module (ECM), sensors, and
actuators for physical damage.
• Inspect ECM grounds for cleanliness, tightness, and
proper location.
• Inspect fuel system for adequate fuel level, and fuel
quality (concerns such as proper octane, contamina-
tion, winter/summer blend).
• Inspect intake air system and air filter for restrictions.
• Inspect battery condition and starter current draw.
If no evidence of a problem is found after visual/physical
engine check has been performed, proceed to MIL DTC
retrieval procedure.
EFI Diagnostics
EFI diagnostics are designed to assist in locating a faulty
circuit or component. When a malfunction is detected by
the Engine Control Module (ECM), a diagnostic trouble
code (DTC) is set and is displayed on the JLG Control
System Analyzer. Refer to Section 6 - JLG Control System
CLEARING TROUBLE CODES
To clear ECM trouble codes, disconnect negative terminal
from battery for approximately 15 minutes.
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 and reference pulses which the ECM
uses to calculate RPM and crankshaft 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 trig-
ger injectors in the proper
sequence. The ECM uses
the CMP signal to indicate
position of the #1 piston
during its power stroke.
T h e C M P u s e s a H a l l
Effect sensor to measure
p i s t o n p o s i t i o n . T h i s
allows the ECM to calcu-
late true sequential fuel injection (SFI) mode of operation.
If the ECM detects an incorrect CMP signal when engine
is running, DTC 53 will set. If CMP signal is lost when
engine is running, the fuel injection system shifts to a cal-
culated sequential fuel injection mode based on the last
fuel injection pulse, and the engine continues to nun. As
long as the fault is present, the engine can be restarted. It
will run in the previously established injection sequence.