Engine Control Module Replacement; Heated Exhaust Gas Oxygen Sensor Replacement; Gm Engine Lpg Fuel System Diagnosis; Fuel System Description - JLG 740AJ Service And Maintenance Manual

SECTION 3 - CHASSIS & TURNTABLE

Engine Control Module Replacement

REMOVAL
1. Disconnect Negative battery cable.
2. Remove controller from mounting bracket.
3. Push connector lock back to unlock connector.
4. Unplug controller and remove.
INSTALLATION
THE CONTROLLER IS CALIBRATED FOR EACH ENGINE VERIFY YOU HAVE THE
CORRECT CONTROLLER
1. Plug connector into controller.
2. Push lock into place.
3. Mount controller into mounting bracket.
4. Reconnect the battery cable.
5. Start engine.
6. Check for any DTC codes and clear.
7. Verify engine is in closed loop and no warning lights are
illuminated.

Heated Exhaust Gas Oxygen Sensor Replacement

REMOVAL
1. Disconnect Negative battery cable.
2. Disconnect the O2 sensor electrical connector.
3. Using an O2 Sensor socket, remove the O2 Sensor and
discard.
INSTALLATION
BEFORE INSTALL THE O2 SENSOR LUBRICATE THREADS WITH ANTI-SEIZE
COMPOUND GM P/N 5613695 OR EQUIVALENT. AVOID GETTING COMPOUND
ON THE SENSOR TIP.
1. Install O2 sensor. Tighten to 30 lb-ft (41 Nm).
2. Start engine.
3. Check for any DTC codes and clear.
4. Verify engine is in closed loop and no warning lights are
illuminated.
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3.35 GM ENGINE LPG FUEL SYSTEM DIAGNOSIS

Fuel System Description

Figure 3-109. EPR Assembly
To maintain fuel and emission control on the LPG fuel system
the Engine Control Units (ECM) relies on numerous engine
sensor and output data from the Electronic Pressure Regulator
(EPR). The ECM will then determine the target fuel calibration
and command the EPR to reposition the voice coil to the
proper position which, subsequently reposition the secondary
lever in the pressure regulator to maintain proper control. The
EPR and ECM will continue to communicate back and forth
during normal operation.
In the event that the EPR fails to communicate or the Commu-
nications Area Network (CAN) cable fails to transmit data the
regulator will operate in an open loop configuration. As the air
valve vacuum in the mixer venturi is communicated to the sec-
ondary chamber of the regulator the secondary diaphragm
will be drawn in a downwards motion. This downward motion
will cause the secondary lever to open thus allowing more fuel
to enter the mixer.
In the (LPR) the fuel is vaporized and the pressure reduced in
two stages. The first stage reduces the pressure to approxi-
mately 1.0 to 3.0 psi (6.8 to 20.6 kPa). The second stage
reduces the pressure to approximately negative 1.5 in. of
water column.
The fuel is then drawn from the secondary chamber of the LPR
by the vacuum generated by air flowing through the mixer.
This vacuum signal is also used to generate lift for the mixer air
valve. This vacuum signal is most commonly referred to as air
valve vacuum. In the mixer, the fuel mixes with the air entering
the engine. This air/ fuel mixture is then drawn into the engine
for combustion.
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