Suzuki 2007 XL7, Service Manual

Page: 310 / 3159

1C-4 Engine Electrical Devices:
Operation
The CMP actuator assembly has an outer housing that is
driven by an engine timing chain. Inside the assembly is
a rotor with fixed vanes that is attached to the camshaft.
Oil pressure that is applied to the fixed vanes will rotate
a specific camshaft in relationship to the crankshaft. The
movement of the intake camshafts will advance the
intake valve timing up to a maximum of 50 crankshaft
degrees. The movement of the exhaust camshafts will
retard the exhaust valve timing up to a maximum of 50
crankshaft degrees. When oil pressure is applied to the
return side of the vanes, the camshafts will return to 0
crankshaft degrees, or top dead center (TDC). The CMP
actuator solenoid valve directs the oil flow that controls
the camshaft movement. The ECM commands the CMP
solenoid to move the solenoid plunger and spool valve
until oil flows from the advance passage (11). Oil flowing
thru the CMP actuator assembly from the CMP solenoid
advance passage applies pressure to the advance side
of the vanes in the CMP actuator assembly. When the
camshaft position is retarded, the CMP actuator solenoid
valve directs oil to flow into the CMP actuator assembly
from the retard passage (3). The ECM can also
command the CMP actuator solenoid valve to stop oil
flow from both passages in order to hold the current
camshaft position.
The ECM operates the CMP actuator solenoid valve by
pulse width modulation (PWM) of the solenoid coil. The
higher the PWM duty cycle, the larger the change in
camshaft timing. The CMP actuator assembly also
contains a lock pin (14) that prevents movement
between the outer housing and the rotor vane assembly.
The lock pin is released by oil pressure before any
movement in the CMP actuator assembly takes place.
The ECM is continuously comparing CMP sensor inputs
with CKP sensor input in order to monitor camshaft
position and detect any system malfunctions. If a
condition exists in either the intake or exhaust camshaft
actuator system, the opposite bank, intake or exhaust,
camshaft actuator will default to 0 crankshaft degrees.
CMP Actuator System Operation
Engine Control Module Description
The engine control module (ECM) interacts with many
more emission related components and systems, and
monitors emission related components and systems for
deterioration. OBD II diagnostics monitor the system
performance and a diagnostic trouble code (DTC) sets if
the system performance degrades.
The malfunction indicator lamp (MIL) operation and the
DTC storage are dictated by the DTC type. A DTC is
ranked as a Type A or Type B if the DTC is emissions
related. Type C is a non-emissions related DTC.
The ECM is in the engine compartment. The ECM is the
control center of the engine controls system. The ECM
controls the following components:
• The fuel injection system
• The ignition system
• The emission control systems
• The on-board diagnostics
• The A/C and fan systems
• The throttle actuation control (TAC) system
The ECM constantly monitors the information from
various sensors and other inputs, and controls the
systems that affect the vehicle performance and the
emissions. The ECM also performs diagnostic tests on
various parts of the system. The ECM can recognize
operational problems and alert the driver via the MIL.
When the ECM detects a malfunction, the ECM stores a
DTC. The condition area is identified by the particular
DTC that is set. This aids the technician in making
repairs.
Driving
Condition
Change in
Camshaft
Position
Objective Result
Idle No Change
Minimize
Valve
Overlap
Stabilize Idle
Speed
Light Engine
Load
Retard Valve
Timing
Decrease
Valve
Overlap
Stable
Engine
Output
Medium
Engine Load
Advance
Valve Timing
Increase
Valve
Overlap
Better Fuel
Economy
with Lower
Emissions
Low to
Medium
RPM with
Heavy Load
Advance
Valve Timing
Advance
Intake Valve
Closing
Improve Low
to Mid-range
Torque
High RPM
with Heavy
Load
Retard Valve
Timing
Retard
Intake Valve
Closing
Improve
Engine
Output
Driving
Condition
Change in
Camshaft
Position
Objective Result