2004 DAEWOO LACETTI brake

4F – 46IANTILOCK BRAKE SYSTEM
DAEWOO V–121 BL4
DTC C0121 – Valve Relay Circuit Malfunction
StepActionValue(s)YesNo
11. Use a scan tool to clear all DTCs.
2. Road test the vehicle.
Does DTC C0121 set again?–Go to Step 3Go to Step 2
21. Check all system wiring harness connectors
and terminals, especially the EBCM, for any
problem that could cause an intermittent condi-
tion.
2. Repair any intermittent problem found.
Is the repair complete?–System OK–
31. Disconnect ABS harness connector J1 from
the EBCM.
2. Examine terminal 19 on the harness connector
and the EBCM connector.
Is there damage or corrosion at terminal 19?–Go to Step 4Go to Step 5
4Repair the terminal or the connector, or replace the
ABS harness or ABS unit as required.
Is the resistance equal to the specified value?–System OK–
5Measure the resistance from terminal 19 of the har-
ness connector J1 to a good chassis ground.
Is the resistance equal to the specified value?
0 WGo to Step 6Go to Step 7
6Replace the ABS unit.
Is the repair complete?–System OK–
7Measure the resistance from terminal 19 of the har-
ness connector J1 to the ground lug at G106.
Is the resistance equal to the specified value?
0 WGo to Step 8Go to Step 9
8Repair the chassis connection at the ground lug.
Is the repair complete?–System OK–
9Repair the open or the high resistance in the ABS
harness, or replace the harness as required.
Is the repair complete?–System OK–

ANTILOCK BRAKE SYSTEM 4F – 47
DAEWOO V–121 BL4
J3B14F10
EBCM
ORN/
BLK
LT BLULT B L U
BLK/ WHT
C201 C202
141
40
19
61
G1062
4
15A Ef13
6
C10211
S30114
C201C110
76
C202 11
DIAGNOSTIC TROUBLE CODE (DTC) C0161
ABS BRAKE SWITCH CIRCUIT MALFUNCTION
Circuit Description
When the brake pedal is depressed, the contacts on the
brake light switch close to illuminate the brake lights. Bat-
tery voltage is also applied to terminal 14 of the electronic
brake control module (EBCM), which signals the ABS con-
troller that the brakes are applied and ABS may be need-
ed. Without this, signals from a wheel speed sensor that
may indicate need for ABS intervention are questionable.
When the brake pedal is not depressed, the EBCM termi-
nal 14 is grounded through the brake lights.
Diagnosis
This procedure will check whether there is no output or
constant output from the brake light switch and will deter-
mine the cause as a faulty switch or a problem in the cir-
cuitry.
Cause(s)
S The ground connection or the positive connection at
the EBCM has failed.
S There is an open, short to ground, or short to posi-
tive in the vehicle wiring.S The brake light switch has failed.
Fail Action
The system records a DTC C0161. ABS and EBD opera-
tion is enabled and ABS / EBD warning lamp don’t turn on.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
1. This simple test will isolate the problem to the fuse–
brake light switch–splice 301 area or the splice
301–EBCM area.
3. This is the first step in identifying an open, a short
to ground, a short to voltage, or a faulty brake light
switch.
11. This step begins the process of finding an open, a
defective connector, or a faulty EBCM.
Diagnostic Aids
Inspect wiring and connectors carefully and thoroughly.
Failure to do so could result in misdiagnosis, causing part
replacement with reappearance of the malfunction.

4F – 48IANTILOCK BRAKE SYSTEM
DAEWOO V–121 BL4
DTC C0161 – ABS Brake Switch Circuit Malfunction
StepActionValue(s)YesNo
1Step on the brake pedal.
Do the brake lights come on at all?–Go to Step 3Go to Step 2
2Remove your foot from the brake pedal.
Do the lights stay on continuously?–Go to Step 8Go to Step 11
3Check fuse EF13 in the engine compartment fuse
block.
Is fuse EF13 blown?–Go to Step 4Go to Step 6
41. Replace fuse EF13.
2. Check the new fuse.
Does the new fuse blow?–Go to Step 5Go to Step 7
51. Repair the short to ground in the brake light
circuitry.
2. Install a new fuse EF13.
Is the repair complete?–System OK–
6Repair the open in the brake light switch circuit ORN/
BLK from terminal 6 of connector C102 at the engine
fuse block to the brake light switch and circuit LT
BLU from terminal 11 of splice S301.
Is the repair complete?–System OK–
7Check for functioning of the brake lights and the ABS
system.
Is the repair complete?–System OK–
8Check the brake light switch on the brake pedal.
Is the switch faulty?–Go to Step 9Go to Step 10
9Repair the brake light switch.
Is the repair complete?–System OK–
10Repair the short to positive in the circuit YEL be-
tween the brake light switch, splice S301, the brake
lights, the center high–mounted stoplamp, and the
ABS wiring harness connector at the EBCM terminal
14.
Is the repair complete?–System OK–
111. Disconnect the EBCM connector.
2. Use a digital voltmeter (DVM) to measure volt-
age between pins 14 and 19 of the ABS har-
ness connector at the EBCM.
3. Have an assistant step on the brake pedal.
Does the DVM indicate the specified value?11–14 vGo to Step 13Go to Step 12

ANTILOCK BRAKE SYSTEM 4F – 49
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
121. Examine the connection between the ABS har-
ness connector and the EBCM connector ter-
minals 14 and 19.
2. Examine the connection at terminal 1 of con-
nector C110.
3. Examine the wiring of circuit LT BLU between
splice S301 and terminal 14 of the ABS EBCM
connector for an open condition.
4. Examine the wiring between ground G106 and
terminal 19 of the ABS EBCM connector.
5. Repair the broken wire or the defective connec-
tor terminal, or replace the connector, the wir-
ing harness as required.
Is the repair complete?–System OK–
13Check the interface between the ABS EBCM con-
nector and the EBCM.
Check the interface between the ABS EBCM con-
nector and the EBCM.–Go to Step 14Go to Step 15
14Repair the connector or replace the wiring harness
or the ABS unit as required.
Is the repair complete?–System OK–
15Replace the ABS unit.
Is the repair complete?–System OK–

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 – 53
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
18Repair the short circuit in the wiring or from a wire to
ground.
Is the repair complete?–System OK–
19Check the continuity of the wiring in both rear 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 8 and 9 at the ABS
connector.
2. The right side uses terminals 1 and 3 at the
ABS connector.
Is continuity good for both harnesses?–Go to Step 21Go to Step 20
20Repair the discontinuity found in the rear wheel
speed sensor wheel speed sensor harness or con-
nector C110.
Is the repair complete?–System OK–
21Replace the ABS unit.
Is the repair complete?–System OK–