Engine Control Module Description; Cmp Actuator System Operation - Suzuki XL7 2007 Service Manual

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

Change in
Driving
Camshaft
Condition
Position
Idle No Change
Light Engine Retard Valve
Load Timing
Medium Advance
Engine Load Valve Timing
Low to
Medium Advance
RPM with Valve Timing
Heavy Load
Objective Result
Minimize
Stabilize Idle
Valve
Speed
Overlap
Decrease Stable
Valve Engine
Overlap Output
Better Fuel
Increase
Economy
Valve
with Lower
Overlap
Emissions
Advance Improve Low
Intake Valve to Mid-range
Closing Torque
Change in
Driving
Camshaft
Condition
Position
High RPM
Retard Valve
with Heavy
Timing
Load

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.
Objective Result
Retard Improve
Intake Valve Engine
Closing Output