2004 DAEWOO LACETTI Sensors

ENGINE CONTROLS 1F – 625
DAEWOO V–121 BL4
EVAPORATIVE EMISSION CANISTER
The Evaporative (EVAP) Emission canister is an emission
control device containing activated charcoal granules.
The EVAP emission canister is used to store fuel vapors
from the fuel tank. Once certain conditions are met, the en-
gine control module (ECM) activates the EVAP canister
purge solenoid, allowing the fuel vapors to be drawn into
the engine cylinders and burned.
POSITIVE CRANKCASE
VENTILATION SYSTEM OPERATION
A Positive Crankcase Ventilation (PCV) system is used to
provide complete use of the crankcase vapors. Fresh air
from the air cleaner is supplied to the crankcase. The fresh
air is mixed with blowby gases which are then passed
through a vacuum hose into the intake manifold.
Periodically inspect the hoses and the clamps. Replace
any crankcase ventilation components as required.
A restricted or plugged PCV hose may cause the following
conditions:
S Rough idle
S Stalling or low idle speed
S Oil leaks
S Oil in the air cleaner
S Sludge in the engine
A leaking PCV hose may cause the following conditions:
S Rough idle
S Stalling
S High idle speed
ENGINE COOLANT TEMPERATURE
SENSOR
The Engine Coolant Temperature (ECT) sensor is a
thermistor (a resistor which changes value based on tem-
perature) mounted in the engine coolant stream. Low cool-
ant temperature produces a high resistance (100,000
ohms at –40 °F [–40 °C]) while high temperature causes
low resistance (70 ohms at 266 °F [130 °C]).
The engine control module (ECM) supplies 5 volts to the
ECT sensor through a resistor in the ECM and measures
the change in voltage. The voltage will be high when the
engine is cold, and low when the engine is hot. By measur-
ing the change in voltage, the ECM can determine the
coolant temperature. The engine coolant temperature af-
fects most of the systems that the ECM controls. A failure
in the ECT sensor circuit should set a diagnostic trouble
code P0117 or P0118. Remember, these diagnostic
trouble codes indicate a failure in the ECT sensor circuit,
so proper use of the chart will lead either to repairing a wir-
ing problem or to replacing the sensor to repair a problem
properly.
THROTTLE POSITION SENSOR
The Throttle Position (TP) sensor is a potentiometer con-
nected to the throttle shaft of the throttle body. The TP sen-
sor electrical circuit consists of a 5 volt supply line and a
ground line, both provided by the engine control module
(ECM). The ECM calculates the throttle position by moni-
toring the voltage on this signal line. The TP sensor output
changes as the accelerator pedal is moved, changing the
throttle valve angle. At a closed throttle position, the output
of the TP sensor is low, about 0.5 volt. As the throttle valve
opens, the output increases so that, at Wide Open Throttle
(WOT), the output voltage will be about 5 volts.
The ECM can determine fuel delivery based on throttle
valve angle (driver demand). A broken or loose TP sensor
can cause intermittent bursts of fuel from the injector and
an unstable idle, because the ECM thinks the throttle is
moving. A problem in any of the TP sensor circuits should
set a diagnostic trouble code (DTC) P0121 or P0122.
Once the DTC is set, the ECM will substitute a default val-
ue for the TP sensor and some vehicle performance will
return. A DTC P0121 will cause a high idle speed.
CATALYST MONITOR OXYGEN
SENSORS
Three–way catalytic converters are used to control emis-
sions of hydrocarbons (HC), carbon monoxide (CO), and
oxides of nitrogen (NOx). The catalyst within the convert-
ers promotes a chemical reaction. This reaction oxidizes
the HC and CO present in the exhaust gas and converts
them into harmless water vapor and carbon dioxide. The
catalyst also reduces NOx by converting it to nitrogen. The
engine control module (ECM) can monitor this process us-
ing the HO2S1 and HO2S2 sensor. These sensors pro-
duce an output signal which indicates the amount of oxy-
gen present in the exhaust gas entering and leaving the
three–way converter. This indicates the catalyst’s ability to
efficiently convert exhaust gasses. If the catalyst is operat-
ing efficiently, the HO2S1 sensor signals will be more ac-
tive than the signals produced by the HO2S2 sensor. The
catalyst monitor sensors operate the same way as the fuel
control sensors. The sensor’s main function is catalyst
monitoring, but they also have a limited role in fuel control.
If a sensor output indicates a voltage either above or below
the 450 mv bias voltage for an extended period of time, the
ECM will make a slight adjustment to fuel trim to ensure
that fuel delivery is correct for catalyst monitoring.
A problem with the HO2S1 sensor circuit will set DTC
P0131, P0132, P0133 or P0134 depending, on the special
condition. A problem with the HO2S2 sensor signal will set
DTC P0137, P0138, P0140 or P0141, depending on the
special condition.
A fault in the Rear Heated Oxygen Sensor (HO2S2) heat-
er element or its ignition feed or ground will result in lower
oxygen sensor response. This may cause incorrect cata-
lyst monitor diagnostic results.

ENGINE CONTROLS 1F – 627
DAEWOO V–121 BL4
A closed throttle on engine coast down produces a rela-
tively low MAP output. MAP is the opposite of vacuum.
When manifold pressure is high, vacuum is low. The MAP
sensor is also used to measure barometric pressure. This
is performed as part of MAP sensor calculations. With the
ignition ON and the engine not running, the engine control
module (ECM) will read the manifold pressure as baromet-
ric pressure and adjust the air/fuel ratio accordingly. This
compensation for altitude allows the system to maintaindriving performance while holding emissions low. The
barometric function will update periodically during steady
driving or under a wide open throttle condition. In the case
of a fault in the barometric portion of the MAP sensor, the
ECM will set to the default value.
A failure in the MAP sensor circuit sets a diagnostic trouble
code P0107 or P0108.
The following tables show the difference between absolute pressure and vacuum related to MAP sensor output, which
appears as the top row of both tables.
MAP
Volts4.94.43.83.32.72.21.71.10.60.30.3
kPa1009080706050403020100
in. Hg29.626.623.720.717.714.811.88.95.92.90
VACUUM
Volts4.94.43.83.32.72.21.71.10.60.30.3
kPa0102030405060708090100
in. Hg02.95.98.911.814.817..720.723.726.729.6
ENGINE CONTROL MODULE
The engine control module (ECM), located inside the pas-
senger kick–panel, is the control center of the fuel injection
system. It constantly looks at the information from various
sensors and controls the systems that affect the vehicle’s
performance. The ECM also performs the diagnostic func-
tions of the system. It can recognize operational problems,
alert the driver through the Malfunction Indicator Lamp
(MIL), and store diagnostic trouble code(s) which identify
problem areas to aid the technician in making repairs.
There are no serviceable parts in the ECM. The calibra-
tions are stored in the ECM in the Programmable Read–
Only Memory (PROM).
The ECM supplies either 5 or 12 volts to power the sensors
or switches. This is done through resistances in the ECM
which are so high in value that a test light will not come on
when connected to the circuit. In some cases, even an or-
dinary shop voltmeter will not give an accurate reading be-
cause its resistance is too low. You must use a digital volt-
meter with a 10 megohm input impedance to get accurate
voltage readings. The ECM controls output circuits such
as the fuel injectors, the idle air control valve, the A/C
clutch relay, etc., by controlling the ground circuit through
transistors or a device called a ”quad–driver.”
FUEL INJECTOR
The Multiport Fuel Injection (MFI) assembly is a solenoid–
operated device controlled by the engine control module
(ECM). It meters pressurized fuel to a single engine cylin-
der. The ECM energizes the fuel injector or the solenoid
to a normally closed ball or pintle valve. This allows fuel toflow into the top of the injector, past the ball or pintle valve,
and through a recessed flow director plate at the injector
outlet.
The director plate has six machined holes that control the
fuel flow, generating a conical spray pattern of finely atom-
ized fuel at the injector tip. Fuel from the tip is directed at
the intake valve, causing it to become further atomized
and vaporized before entering the combustion chamber.
A fuel injector which is stuck partially open will cause a loss
of fuel pressure after the engine is shut down. Also, an ex-
tended crank time will be noticed on some engines. Diesel-
ing can also occur because some fuel can be delivered to
the engine after the ignition is turned OFF.
KNOCK SENSOR
The knock sensor detects abnormal knocking in the en-
gine. The sensor is mounted in the engine block near the
cylinders. The sensor produces an AC output voltage
which increases with the severity of the knock. This signal
is sent to the engine control module (ECM). The ECM then
adjusts the ignition timing to reduce the spark knock.
ROUGH ROAD SENSOR
The engine control module (ECM) receives rough road in-
formation from the VR sensor. The ECM uses the rough
road information to enable or disable the misfire diagnos-
tic. The misfire diagnostic can be greatly affected by
crankshaft speed variations caused by driving on rough
road surfaces. The VR sensor generates rough road infor-
mation by producing a signal which is proportional to the
movement of a small metal bar inside the sensor.
If a fault occurs which causes the ECM to not receive
rough road information between 30 and 80 mph (50 and
132 km/h), DTC P1391 will set.

1F – 630IENGINE CONTROLS
DAEWOO V–121 BL4
COMPREHENSIVE COMPONENT
MONITOR DIAGNOSTIC OPERATION
Comprehensive component monitoring diagnostics are
required to monitor emissions–related input and output
powertrain components.
Input Components
Input components are monitored for circuit continuity and
out–of–range values. This includes rationality checking.
Rationality checking refers to indicating a fault when the
signal from a sensor does not seem reasonable, i.e.
Throttle Position (TP) sensor that indicates high throttle
position at low engine loads or Manifold Absolute Pressure
(MAP) voltage. Input components may include, but are not
limited to, the following sensors:
S Vehicle Speed Sensor (VSS).
S Crankshaft Position (CKP) sensor.
S Throttle Position (TP) sensor.
S Engine Coolant Temperature (ECT) sensor.
S Camshaft Position (CMP) sensor.
S Manifold Absolute Pressure (MAP) sensor.
In addition to the circuit continuity and rationality check,
the ECT sensor is monitored for its ability to achieve a
steady state temperature to enable closed loop fuel con-
trol.
Output Components
Output components are diagnosed for proper response to
control module commands. Components where functional
monitoring is not feasible will be monitored for circuit conti-
nuity and out–of–range values if applicable. Output com-
ponents to be monitored include, but are not limited to the
following circuit:
S Idle Air Control (IAC) Motor.
S Control module controlled EVAP Canister Purge
Valve.
S A/C relays.
S Cooling fan relay.
S VSS output.
S MIL control.
Refer to ”Engine Control Module” and Sensors in this sec-
tion.
Passive and Active Diagnostic Tests
A passive test is a diagnostic test which simply monitors
a vehicle system or component. Conversely, an active
test, actually takes some sort of action when performing
diagnostic functions, often in response to a failed passive
test. For example, the Exhaust Gas Recirculation (EGR)
diagnostic active test will force the EGR valve open during
closed throttle deceleration and/or force the EGR valve
closed during a steady state. Either action should result in
a change in manifold pressure.
Intrusive Diagnostic Tests
This is any on–board test run by the Diagnostic Manage-
ment System which may have an effect on vehicle perfor-
mance or emission levels.
Warm–Up Cycle
A warm–up cycle means that engine temperature must
reach aminimum of 160°F (70°C) and rise at least 72°F
(22°C) over the course of a trip.
Freeze Frame
Freeze Frame is an element of the Diagnostic Manage-
ment System which stores various vehicle information at
the moment an emissions–related fault is stored in
memory and when the Malfunction Indicator Lamp (MIL)
is commanded on. These data can help to identify the
cause of a fault.
Failure Records
Failure Records data is an enhancement of the EOBD
Freeze Frame feature. Failure Records store the same ve-
hicle information as does Freeze Frame, but it will store
that information for any fault which is stored in onboard
memory, while Freeze Frame stores information only for
emission–related faults that command the MIL on.
COMMON EOBD TERMS
Diagnostic
When used as a noun, the word diagnostic refers to any
on–board test run by the vehicle’s Diagnostic Manage-
ment System. A diagnostic is simply a test run on a system
or component to determine if the system or component is
operating according to specification. There are many diag-
nostics, shown in the following list:
S Misfire
S Front Heated Oxygen Sensor (HO2S1)
S Rear Heated Oxygen Sensor (HO2S2)
S Exhaust Gas Recirculation (EGR)
S Catalyst monitoring
Enable Criteria
The term ”enable criteria” is engineering language for the
conditions necessary for a given diagnostic test to run.
Each diagnostic has a specific list of conditions which
must be met before the diagnostic will run.
”Enable criteria” is another way of saying ”conditions re-
quired.”
The enable criteria for each diagnostic is listed on the first
page of the Diagnostic Trouble Code (DTC) description
under the heading ”Conditions for Setting the DTC.” En-
able criteria varies with each diagnostic and typically in-
cludes, but is not limited to, the following items:
S Engine speed.
S Vehicle speed
S Engine Coolant Temperature (ECT)
S Manifold Absolute Pressure (MAP)

SECTION : 4F
ANTILOCK BRAKE SYSTEM
CAUTION : Disconnect the negative battery cable before removing or installing any electrical unit or when a tool
or equipment could easily come in contact with exposed electrical terminals. Disconnecting this cable will help
prevent personal injury and damage to the vehicle. The ignition must also be in LOCK unless otherwise noted.
TABLE OF CONTENTS
SPECIFICATIONS4F–2 . . . . . . . . . . . . . . . . . . . . . . . . . .
Fastener Tightening Specifications 4F–2. . . . . . . . . .
SPECIAL TOOLS4F–2 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Special Tools Table 4F–2. . . . . . . . . . . . . . . . . . . . . . . .
SCHEMATIC AND ROUTING DIAGRAMS4F–3 . . . . .
Abs System Circuit (I) 4F–3. . . . . . . . . . . . . . . . . . . . . .
Abs System Circuit (II) 4F–4. . . . . . . . . . . . . . . . . . . . .
Ebcm Connector Face View 4F–5. . . . . . . . . . . . . . . . .
COMPONENT LOCATOR4F–6 . . . . . . . . . . . . . . . . . . . .
ABS/EBD System Drive 4F–6. . . . . . . . . . . . . . . . . . . .
DIAGNOSIS4F–7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diagnostic Circuit Check 4F–7. . . . . . . . . . . . . . . . . . .
ABS Indicator Lamp Inoperative 4F–9. . . . . . . . . . . . .
Power Supply to Control Module,
No DTCs Stored 4F–12. . . . . . . . . . . . . . . . . . . . . . . .
ABS Indicator Lamp Illuminated Continuously,
No DTCs Stored 4F–16. . . . . . . . . . . . . . . . . . . . . . . .
Electronic Brake–Force Distribution (EBD)
System Indicator Lamp Inoperative 4F–18. . . . . . . .
SELF–DIAGNOSTICS 4F–22. . . . . . . . . . . . . . . . . . . .
DISPLAYING DTCs 4F–22. . . . . . . . . . . . . . . . . . . . . . .
CLEARING DTCs 4F–22. . . . . . . . . . . . . . . . . . . . . . . .
INTERMITTENTS AND POOR
CONNECTIONS 4F–22. . . . . . . . . . . . . . . . . . . . . . . .
DTC C0035 Left Front Wheel Speed Sensor
Circuit Malfunction 4F–23. . . . . . . . . . . . . . . . . . . . . .
DTC C0040 Right Front Wheel Speed Sensor
Circuit Malfunction 4F–26. . . . . . . . . . . . . . . . . . . . . .
DTC C0045 Left Rear Wheel Speed Sensor
Circuit Malfunction 4F–29. . . . . . . . . . . . . . . . . . . . . .
DTC C0050 Right Rear Wheel Speed Sensor
Circuit Malfunction 4F–32. . . . . . . . . . . . . . . . . . . . . .
DTC C0060/C0065 Left Front Inlet and
Outlet Valve Solenoid Fault 4F–35. . . . . . . . . . . . . . .
DTC C0070/C0075 Right Front Inlet and
Outlet Valve Solenoid Fault 4F–37. . . . . . . . . . . . . . . DTC C0080/C0085 Left Rear Inlet and
Outlet Valve Solenoid Fault 4F–39. . . . . . . . . . . . . . .
DTC C0090/C0095 Right Rear Inlet and
Outlet Valve Solenoid Fault 4F–41. . . . . . . . . . . . . . .
DTC C0110 Pump Motor Circuit Malfunction 4F–43. .
DTC C0121 Valve Relay Circuit Malfunction 4F–45. .
DTC C0161 ABS Brake Switch Circuit
Malfunction 4F–47. . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC C0245 Wheel Speed Sensor Frequency
Error 4F–50. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC C0550 ABS Control Module Internal
Fault 4F–54. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC C0800 Low Voltage Fault 4F–56. . . . . . . . . . . . .
DTC C0931 Overheated 4F–59. . . . . . . . . . . . . . . . . . .
MAINTENANCE AND REPAIR4F–60 . . . . . . . . . . . . . .
ON–VEHICLE SERVICE 4F–60. . . . . . . . . . . . . . . . . . . .
Service Precautions 4F–60. . . . . . . . . . . . . . . . . . . . . . .
Bleeding System 4F–61. . . . . . . . . . . . . . . . . . . . . . . . .
ABS 5.3 Assembly 4F–61. . . . . . . . . . . . . . . . . . . . . . . .
Front Wheel Speed Sensor 4F–62. . . . . . . . . . . . . . . .
Front Wheel Speed Sensor Jumper Harness 4F–63.
Rear Wheel Speed Sensor 4F–64. . . . . . . . . . . . . . . . .
GENERAL DESCRIPTION AND SYSTEM
OPERATION4F–65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Basic Knowledge Required 4F–65. . . . . . . . . . . . . . . . .
ABS System Components 4F–65. . . . . . . . . . . . . . . . .
Base Braking Mode 4F–65. . . . . . . . . . . . . . . . . . . . . . .
Antilock Braking Mode 4F–66. . . . . . . . . . . . . . . . . . . . .
EBD System 4F–69. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electronic Brake–Force Distribution (EBD) Failure
Matrix 4F–70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tires and ABS/EBD 4F–71. . . . . . . . . . . . . . . . . . . . . . .
Electronic Brake Control Module (EBCM) 4F–71. . . .
Front Wheel Speed Sensors 4F–71. . . . . . . . . . . . . . .
Front Wheel Speed Sensor Rings 4F–71. . . . . . . . . . .
Rear Wheel Speed Sensors and Rings 4F–71. . . . . .
Valve Relay and Pump Motor Relay 4F–71. . . . . . . . .

4F – 50IANTILOCK BRAKE SYSTEM
DAEWOO V–121 BL4
J3B14F11
Left Front Left RearRight Front
Right Rear
EBCM
BRN LT
BLU1
2
6
7
PPL
GRYGRY GRY
YEL
C111
WHT 1
12
2
44
55WHT WHT1
1 2
43
89
Wheel Speed Sensors
BRNBRN DK
BLUBLK
BLK REDC302
C110 WHT
WHT1 2
2
110
33
DIAGNOSTIC TROUBLE CODE (DTC) C0245
WHEEL SPEED SENSOR FREQUENCY ERROR
Circuit Description
The toothed wheel generates a voltage pulse as it moves
past the wheel speed sensor. Each tooth–gap–tooth se-
ries on the wheel generates the pulses. The electronic
brake control module (EBCM) uses the frequency of these
pulses to determine wheel speed. The voltage generated
depends on the air gap between the wheel speed sensor
and the toothed wheel, and on the wheel speed.
Diagnosis
This DTC will set when the EBCM cannot identify which
wheel speed sensor is causing the malfunction. It is nec-
essary to check all wheel speed sensors and associated
wiring to determine the cause of the DTC.
Cause(s)
S Incorrect number of teeth on the toothed wheel.
S Damaged or broken teeth on the toothed wheel.
S Discontinuity or short in wheel speed sensor wiring.
Fail Action
Antilock brake system (ABS) action is disabled and the
ABS warning lamp is ON.Test Description
The number(s) below refer to step(s) on the diagnostic
table.
1. This step begins the examination of the front wheel
speed sensors.
3. This step checks for a problem with one of the front
toothed rings.
5. This step checks the front wheel speed sensors.
7. This step checks for shorts in a front wheel speed
sensor harness.
9. This step checks for opens in a front wheel speed
sensor harness.
11. This step begins a check of the rear wheel speed
sensors.
13. This step checks for a problem with one of the rear
toothed rings.
15. This step checks the rear wheel speed sensors.
17. This step checks for shorts in a rear wheel speed
sensor harness.
19. This step checks for opens in a rear wheel speed
sensor harness.

ANTILOCK BRAKE SYSTEM 4F – 51
DAEWOO V–121 BL4
Diagnostic Aids
DTC C0245 may be set by running the scan tool auto test
if the throttle angle readings are not updating while in the
data list mode. If this is the case, clear the DTCs, discon-
nect the scan tool, and road test the vehicle to at least 12
km/h (7 mph) to see if the DTC resets.
Check the toothed wheels for any large grooves, gouges,
marks, etc. that might influence the tooth’s signal at the
wheel speed sensor. Also check for a buildup of foreignmaterial in the gaps between teeth in the toothed wheel,
this material may cause this malfunction.
A badly worn hub/bearing assembly may cause this mal-
function. The wheel speed sensor–to–toothed wheel air
gap may change excessively due to bearing play.
If an improper rear hub assembly or front outer constant
velocity joint is installed, one with a toothed wheel contain-
ing the incorrect number of teeth, this DTC can set. Be
sure that the front and the rear toothed wheel have 47 and
29 teeth.
DTC C0245 – Wheel Speed Sensor Frequency Error
StepActionValue(s)YesNo
1Visually inspect the wiring for the front wheel speed
sensors.
Is there any damage?–Go to Step 2Go to Step 3
2Check that the correct outer constant velocity (CV)
joints are installed on the vehicle. The front speed
rings have 47 teeth and the rear speed rings have 29
theeth.
Is the repair complete?–System OK–
3Check fuse EF2 in the engine fuse block.
Is one of these incorrect?–Go to Step 4Go to Step 5
4Replace the incorrect outer CV joint with the proper
unit.
Is the repair complete?–System OK–
51. Disconnect the wheel speed sensor harnesses
from the wheel speed sensor connectors.
2. Measure the wheel speed sensor resistance at
the wheel speed sensor connector terminals.
Does the resistance fall within the specified values
for both wheel speed sensors?1280–1920 WGo to Step 7Go to Step 6
6Replace the faulty wheel speed sensor.
Is the repair complete?–System OK–
71. Disconnect ABS control module connector.
2. Check each wheel speed sensor harness for a
short circuit between its wires with a digital
ohmmeter attached to the two terminals at the
harness side of the wheel speed sensor con-
nector.
3. Also check each wheel speed sensor harness
wire for a short to ground from the connector
terminals.
Is there any short circuit in either wheel speed sen-
sor harness?–Go to Step 8Go to Step 9
8Repair the short circuit in the wiring or from a wiring
harness to ground.
Is the repair complete?–System OK–

4F – 52IANTILOCK BRAKE SYSTEM
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
9Check the continuity of the wiring in both front wheel
speed sensor circuits between the ABS connector
and the wheel speed sensor wheel speed sensor
connector on each side of the vehicle.
1. The left side uses terminals 6 and 7 at the ABS
connector.
2. The right side uses terminals 4 and 5 at the
ABS connector.
Is continuity good for both harnesses?–Go to Step 11Go to Step 10
10Repair the discontinuity found in the front wheel
speed sensor harness.
Is the repair complete?–System OK–
111. Visually inspect the wiring for the rear wheel
speed sensors.
2. Check that the wheel speed sensors are prop-
erly mounted and that the retaining bolts are
properly tightened.
Is there any damage?–Go to Step 12Go to Step 13
12Repair or replace components as required.
Is the repair complete?–System OK–
13Remove each wheel speed sensor from the rear
knuckles and inspect the toothed ring through the
wheel speed sensor mounting holes.
1. Check for any damaged or missing teeth.
2. Check that the ring is properly positioned under
the wheel speed sensor.
Is there any damage or other fault with either speed
ring?–Go to Step 14Go to Step 15
14Replace the rear wheel hub with the proper unit.
Is the repair complete?–System OK–
151. Disconnect the rear wheel speed sensor har-
nesses from the wheel speed sensor connec-
tors.
2. Measure the wheel speed sensor resistance at
the wheel speed sensor connector terminals.
Does the resistance fall within the specified values
for both wheel speed sensors?1280–1920 WGo to Step 17Go to Step 16
16Replace the faulty wheel speed sensor.
Is the repair complete?–System OK–
171. The ABS control module connector should still
be disconnected. Disconnect it now if it is not.
2. Check each wheel speed sensor harness for a
short circuit between its wires with a digital
ohmmeter attached to the two terminals at the
harness side of the wheel speed sensor con-
nector.
3. Also check each wheel speed sensor harness
wire for a short to ground from the connector
terminals.
Is there any short circuit in either wheel speed sen-
sor harness?–Go to Step 18Go to Step 19

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.