JLG 800A_AJ Service Manual - Manual (Page 149)

SECTION 3 - CHASSIS & TURNTABLE
3120858 – 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 diagnos-
tic trouble code (DTC) is set and the Malfunction Indicator
Lamp (MIL) will be illuminated.
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 seconds 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
following 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 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. 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.
Figure 3-54. Malfunction Indicator and Test Button