DAEWOO LACETTI 2004 Service Repair Manual

4F – 60IANTILOCK BRAKE SYSTEM
DAEWOO V–121 BL4
MAINTENANCE AND REPAIR
ON–VEHICLE SERVICE
SERVICE PRECAUTIONS
CAUTION : Brake fluid may irritate eyes and skin. In
case of contact, take the following actions:
S Eye contact – rinse thoroughly with water.
S Skin contact – wash with soap and water.
S Ingestion – consult a physician immediately.
CAUTION : To help avoid personal injury due to poor
braking, DO NOT tap into the vehicle’s brake system
to operate a trailer brake system.
Notice : When fasteners are removed, always reinstall
them at the same location from which they were removed.
If a fastener needs to be replaced, use the correct part
number fastener for that application. If the correct part
number fastener is not available, a fastener of equal size
and strength (or stronger) may be used. Fasteners that
are not reused, and those requiring thread–locking com-
pound will be called out. The correct torque values must
be used when installing fasteners that require them. If the
above procedures are not followed, parts or system dam-
age could result.
Notice : Use only DOT 3 equivalent hydraulic brake fluid.
The use of DOT 5 (silicone) brake fluid is not recom-
mended. Reduced brake performance or durability may
result.
Notice : Avoid spilling brake fluid on any of the vehicle’s
painted surfaces, wiring, cables, or electrical connectors.
Brake fluid will damage paint and electrical connections.
If any fluid is spilled on the vehicle, flush the area with wa-
ter to lessen the damage.
Computer System Service Precautions
Take care to avoid electronic brake control module
(EBCM) circuit overloading. In testing for opens or shorts,
do not ground or apply voltage to any circuit unless
instructed to do so by the diagnostic procedure. Test cir-
cuits only with a high–impedance multimeter. Never re-
move or apply power to any control module with the igni-
tion switch in the ON position. Always turn the ignition to
the OFF position before removing or connecting battery
cables, fuses, or connectors.
General Service Precautions
S Disconnect the EBCM connector before performing
any vehicle welding work using an electric arc weld-
er.
S Do not attempt to disassemble any component des-
ignated as nonserviceable. The hydraulic modulator
and the EBCM can be separated from each other
and replaced separately but cannot be serviced.
They have no replaceable parts, and there is no
access to the components they contain.

ANTILOCK BRAKE SYSTEM 4F – 61
DAEWOO V–121 BL4
BLEEDING SYSTEM
Replacement modulators are shipped already filled and
bled. In normal procedures requiring removal of the modu-
lator, such as to replace the EBCM, air will not enter the
modulator, and normal bleeding will be all that is needed.
For this procedure, refer to Section 4A, Hydraulic Brakes.
If air enters the hydraulic modulator, or if an unfilled modu-
lator is installed, use the brake bleeding program in the
scan tool to bleed the modulator. Manual bleeding of the
hydraulic modulator is not possible.
ABS 5.3 ASSEMBLY
(Left–Hand Drive Shown, Right–Hand Drive
Similar)
Removal Procedure
1. Disconnect the negative battery cable.
2. Disconnect the 31–pin ABS wiring harness connec-
tor from its socket on the EBCM.
3. Cover the connector and the socket with shop
cloths to protect them from brake fluid.
Notice : Take care not to allow air into the hydraulic unit
or into the brake pipes from the master cylinder. If air gets
into the hydraulic unit, it will require a bleeding procedure
using a scan tool programmed for the ABS 5.3 system. As
long as no air enters the hydraulic unit, a simple bleeding
procedure is all the system will require.
4. Remove the brake pipes from the hydraulic unit. It
may be necessary to loosen the brake pipe nuts on
the master cylinder to allow for moving those pipes
out of the way.
5. Loosen the mounting nuts on the hydraulic unit.
6. Move the brake pipes aside far enough to allow for
lifting the ABS 5.3 unit out of the mounting bracket.
7. Tighten the brake pipe nuts on the master cylinder
to avoid leaking brake fluid.
8. Cap the brake pipes.
Installation Procedure
1. Insert the ABS 5.3 hydraulic unit into its mounting
bracket and install the nuts.
Tighten
Tighten the ABS 5.3 mounting nuts to 15 NSm (11 lb–
ft).
2. Remove the screw plugs and install all of the hy-
draulic brake pipes.
Tighten
Tighten the brake pipe nuts to 22 NSm (16 lb–ft).
3. Connect the 31–pin wiring harness connector J1.
4. Connect the negative battery cable.
5. Bleed the hydraulic system. Refer to Section 4A,
Hydraulic Brakes.

4F – 62IANTILOCK BRAKE SYSTEM
DAEWOO V–121 BL4
FRONT WHEEL SPEED SENSOR
Removal Procedure
1. Disconnect the negative battery cable.
2. Disconnect the front wheel speed sensor electrical
connector.
3. Raise and suitably support the vehicle.
4. Remove the wheel. Refer to Section 2E, Tires and
Wheels.
5. Turn the steering wheel to expose the speed sen-
sor. It is located at the rear of the steering knuckle
near the tie rod end.
6. Remove the bolt and the front wheel speed sensor
from the steering knuckle.
7. Free the feedthrough grommet for the speed sen-
sor harness and the hydraulic pipe from the strut
tower. Remove the speed sensor harness from it so
that the connector can pass through the hole in the
strut tower.
8. Free the sensor harness from the grommet holders
and the clamps and pull it through the fender.
Installation Procedure
1. Install the front wheel speed sensor to the steering
knuckle. Secure it with the bolt.
Tighten
Tighten the front wheel speed sensor bolt to 8 NSm
(71 lb–in).
2. Feed the sensor harness into the engine compart-
ment, insert it into the grommet, and secure the
grommet into the hole in the strut tower.
3. Secure the harness into the grommet holders and
the clamps under the fender.
4. Install the wheel. Refer to Section 2E, Tires and
Wheels.
5. Lower the vehicle.
6. Connect the front wheel speed sensor electrical
connector.
7. Connect the negative battery cable.

ANTILOCK BRAKE SYSTEM 4F – 63
DAEWOO V–121 BL4
FRONT WHEEL SPEED SENSOR
JUMPER HARNESS
(Left–Hand Drive Shown, Right–Hand Drive
Similar)
Removal Procedure
1. Disconnect the negative battery cable.
2. Disconnect connector from the EBCM.
3. Remove the appropriate terminals from connector:
S Right–side – terminals 4 (WHT) and 5 (GRY).
S Left–side – terminals 6 (BRN) and 7 (LT BLU).
4. Both speed sensor harnesses break out of the ABS
wiring harness just beyond the ABS connector. The
right–side speed sensor harness crosses the top of
the fire wall to the right–side fender area. The left–
side speed sensor harness goes directly to the left–
side fender area.
5. Free the speed sensor harness from the wiring har-
ness.
6. Remove the front wheel speed sensor electrical
connector from the retaining clamps and disconnect
the harness from the sensor connector.
Installation Procedure
1. Install the front wheel speed sensor jumper har-
ness.
2. Connect the front wheel speed sensor electrical
connector and secure it into the clamps.
3. Replace the jumper harness into the wiring har-
ness.
4. Insert the terminals into connector as they had
been removed:
S Right–side – terminals 4 (WHT) and 5 (GRY).
S Left–side – terminals 6 (BRN) and 7 (LT BLU).
5. Connect EBCM connector.
6. Connect the negative battery cable.

4F – 64IANTILOCK BRAKE SYSTEM
DAEWOO V–121 BL4
REAR WHEEL SPEED SENSOR
Removal Procedure
1. Disconnect the negative battery cable.
2. Raise and suitably support the vehicle.
3. Disconnect the rear wheel speed sensor electrical
connector.
4. Remove the rear hub unit from the knuckle assem-
bly, because the wheel speed sensor is not service-
able separately.
Installation Procedure
1. Install the rear hub unit to the knuckle assembly.
Tighten
Tighten the rear hub unit to the knuckle assembly to
65 NSm (48 lb–ft).
2. Connect the rear wheel speed sensor electrical
connector.

ANTILOCK BRAKE SYSTEM 4F – 65
DAEWOO V–121 BL4
GENERAL DESCRIPTION AND SYSTEM
OPERATION
BASIC KNOWLEDGE REQUIRED
Before using this section, it is important that you have a ba-
sic knowledge of the following items. Without this knowl-
edge, it will be difficult to use the diagnostic procedures
contained in this section.
S Basic Electrical Circuits : You should understand
the basic theory of electricity and know the mean-
ing of voltage, current (amps), and resistance
(ohms). You should understand what happens in a
circuit with an open or shorted wire. You should be
able to read and understand a wiring diagram.
S Use of Circuit Testing Tools : You should know how
to use a test light and how to bypass components
to test circuits using fused jumper wires. You should
be familiar with a digital multimeter. You should be
able to measure voltage, resistance, and current,
and be familiar with the controls and how to use
them correctly.
ABS SYSTEM COMPONENTS
The ABS 5.3 Antilock Braking System (ABS) consists of
a conventional hydraulic brake system plus antilock com-
ponents. The conventional brake system includes a vacu-
um booster, master cylinder, front disc brakes, rear lead-
ing/trailing drum brakes, interconnecting hydraulic brake
pipes and hoses, brake fluid level sensor and the BRAKE
indicator.
The ABS components include a hydraulic unit, an elec-
tronic brake control module (EBCM), two system fuses,
four wheel speed sensors (one at each wheel), intercon-
necting wiring, the ABS indicator, the EBD indicator (which
is connected to the parking lamp) and the rear disk brakes.
See “ABS Component Locator” in this section for the gen-
eral layout of this system.
The hydraulic unit with the attached EBCM is located be-
tween the surge tank and the fire wall on the left side of the
vehicle.
The basic hydraulic unit configuration consists of hydraulic
check valves, two solenoid valves for each wheel, a hy-
draulic pump, two accumulators, and two damper. The hy-
draulic unit controls hydraulic pressure to the front calipers
and rear wheel cylinders by modulating hydraulic pressure
to prevent wheel lockup.
Nothing in the hydraulic unit or the EBCM is serviceable.
In the event of any failure, the entire ABS unit with at-
tached EBCM must be replaced. For more information, re-
fer to ”Base Braking Mode” and ”Antilock Braking Mode”
in this section.
BASE BRAKING MODE
The baseline braking mode of the ABS 5.3 system used
in this vehicle is a diagonal split system. In this system,
one master cylinder circuit supplies pressure to the right
front and the left rear brakes; the other circuit supplies
pressure to the left front and the right rear brakes. All
valves in the hydraulic modulator are in their normal, non–
energized positions as shown in the drawings found in
”ABS System Components” in this section.

4F – 66IANTILOCK BRAKE SYSTEM
DAEWOO V–121 BL4
1. Check Valve
2. Inlet Valve
3. Outlet Valve
4. Pump
5. Accumulator
6. Damper7. Pump Motor
8. Hydraulic Circuit 2
9. Hydraulic Circuit 1
10. Master Cylinder
11. Master Cylinder Reservoir
ANTILOCK BRAKING MODE – APPLY
If a wheel speed sensor detects a wheel locking up, the
electronic brake control module (EBCM) closes the nor-
mally open inlet valve for the brake on that wheel to pre-
vent adding more hydraulic pressure to that brake.

ANTILOCK BRAKE SYSTEM 4F – 67
DAEWOO V–121 BL4
ANTILOCK BRAKING MODE – HOLD
The illustration shows this for the right front brake.

4F – 68IANTILOCK BRAKE SYSTEM
DAEWOO V–121 BL4
ANTILOCK BRAKING MODE –
RELEASE
If the wheel locking tendency continues, the EBCM re-
leases the hydraulic pressure at that brake by opening the
outlet valve for that wheel.

ANTILOCK BRAKE SYSTEM 4F – 69
DAEWOO V–121 BL4
EBD (ELECTRONIC BRAKE FORCE
DISTRIBUTION) SYSTEM
As an add–on logic to the ABS base algorithm, EBD works
in a range in which the intervention thresholds for ABS
control are not reached yet.
EBD ensures that the rear wheels are sensitively moni-
tored for slip with respect to the front axle. If slip is de-
tected, the inlet valves for the rear wheels are switched to
pressure hold to prevent a further increase in pressure at
the rear–wheel breaks, thus electronically reproducing a
pressure–reduction function at the rear–wheel brakes.
THE BENEFITS OF EBD
S Elimination of conventional proportioning valve.
S EBD utilizes the existing rear axle wheel speed
sensor to monitor rear wheel slip.
S Based on many variables in algorithm a pressure
hold, increase and/or decrease pulsetrain may be
triggered at the rear wheels insuring vehicle stabil-
ity.
S Vehicle approaches the ideal brake force distribu-
tion. (front to rear)
S Constant brake force distribution during vehicle life-
time.
S EBD function is monitored via ABS safety logic.
(conventional proportioning valves are not monitor-
able)
S ”Keep alive” function.