Suzuki XL7 2007 Service Manual page 1417

Line Pressure Control Solenoid Valve (SLT)
(316)
The line pressure control solenoid valve (normally high,
3-port linear pressure control solenoid) is a precision
electronic pressure regulator that controls transmission
line pressure based on current flow through its coil
windings. As current flow is increased, the magnetic field
produced by the coil moves the solenoid's plunger
further away from the exhaust port. Opening the exhaust
port decreases the output fluid pressure regulated by the
line pressure control solenoid valve, which ultimately
decreases line pressure. The TCM controls the line
pressure control solenoid valve based on various inputs
including throttle position, transmission fluid temperature
and gear state.
Duty Cycle, Frequency and Current Flow
A "duty cycle" may be defined as the percentage of time
current is flowing through a solenoid coil during each
cycle. The number of cycles that occur within a specified
amount of time, usually measured in seconds, is called
"frequency". Typically, the operation of an electronically
controlled pulse width modulated solenoid is explained
in terms of duty cycle and frequency.
The TCM controls the line pressure control solenoid
valve on a positive duty cycle at a fixed frequency of
292.5 Hz (cycles-per-second). A higher duty cycle
provides a greater current flow through the solenoid. The
high (positive) side of the line pressure control solenoid
valve electrical circuit at the TCM controls the line
pressure control solenoid valve operation. The TCM
provides a ground path for the circuit, monitors average
current and continuously varies the line pressure control
solenoid valve duty cycle to maintain the correct average
current flowing through the line pressure control solenoid
valve.
Duty Cycle Current
Minimum 0.1 amps
Maximum 1.1 amps
Line pressure control solenoid valve resistance should
measure between 5.0 and 5.6 ohms when measured at
20°C (68°F).
The duty cycle and current flow to the line pressure
control solenoid valve are mainly affected by throttle
position (engine torque) and they are inversely
proportional to throttle angle (engine torque). In other
words, as the throttle angle (engine torque) increases,
the duty cycle is decreased by the TCM which
decreases current flow to the line pressure control
solenoid valve. Current flow to the line pressure control
solenoid valve creates a magnetic field that moves the
solenoid plunger against spring force.
TCC Lock Up Pressure Control Solenoid Valve
(SLU) (339)
The TCC lock up pressure control solenoid valve is a
normally low, 3-port linear pressure control solenoid
used to control the apply and release of the 2nd (B2) and
low and reverse (B3) clutches, and the torque converter
clutch. The TCM operates the solenoid with a negative
duty cycle at a fixed frequency of 32 Hz to control the
rate of clutch apply/release. The solenoid's ability to
"ramp" the clutch apply and release pressures results in
a smoother clutch operation.
When vehicle operating conditions are appropriate to
apply the TCC, the TCM increases the duty cycle to
allow the TCC lock up pressure control solenoid valve to
command lock up control (12) and TCC signal (13) fluid
pressure at a level sufficient to move the lock up relay
valve and the lock up control valve to the apply position.
Release (4) fluid pressure is directed to exhaust, and
apply (5) fluid is directed to the apply side of the
converter pressure plate/damper assembly. The TCM
then increases the duty cycle to control a slippage of 20-
80 RPM between the pressure plate/damper assembly
Line Pressure
and the converter cover. This provides for improved
Maximum
filtration of engine vibrations and allows the TCC to
Minimum
apply at low engine speeds in 2nd, 3rd, 4th and 5th gear.
Automatic Transmission: 5A-7