SECTION 3 - CHASSIS & TURNTABLE
3120740
– JLG Lift –
3-93
EFI Diagnostics (Prior to S/N 0300065534)
The 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 the Malfunction Indicator Lamp (MIL) will be illumi-
nated.
MIL DTC RETRIEVAL
Diagnostic trouble codes (DTCs) can be retrieved by pushing
and holding the test button on the side of the ground control
box. The Malfunction Indicator Light will illuminate for 2-3 sec-
onds when the key is positioned to the on position to act as a
self-test. If a DTC is present, the light will illuminate and stay
on.
When reading Diagnostic Trouble Codes thru the MIL, the fol-
lowing conditions apply:
• The flashing MIL is on for 0.4 second and off for 0.4 second.
• The MIL is off for 1.2 seconds between digits of two digit
DTCs.
• The MIL is off for 2.4 seconds between DTCs.
• Each DTC repeats 3 times before the next stored DTC
begins flashing.
• Up to 6 DTCs can be stored.
• Once all stored DTCs are flashed, the process repeats with
the first stored DTC.
• DTCs are stored in the order in which they were set.
CLEARING TROUBLE CODES
To clear the trouble codes from the ECM, the electrical current
running to the ECM must be shut off. To do this, disconnect
the negative terminal from the battery for a period of approxi-
mately 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. The CKP sensor initiates the 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 trigger the
injectors in the proper sequence. The ECM uses the CMP signal
to indicate the position of the #1 piston 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 operation. If the ECM detects an incor-
rect 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 injec-
tion 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 estab-
lished injection sequence.
Figure 3-54. Malfunction Indicator and Test Button
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