2003 HONDA CIVIC wheel

ABS Control Unit
Main Control
The ABS control unit detects the wheel speed based on the wheel sensor signal it received, then it calculates the
vehicle speed based on the detected wheel speed. The control unit detects the vehicle speed during deceleration
based on the rate of deceleration.
The ABS control unit calculates the slip rate of each wheel and transmits the control signal to the modulator unit
solenoid valve when the slip rate is high.
The pressure reduction control has three modes: pressure reducing, pressure retaining, and pressure intensifying.
Self-diagnosis Function
1. TheABScontrol unitisequippedwithamainCPUandasub-CPU.EachCPUcheckstheotherforproblems.
2. The CPUS check the circuit of the system.
3. TheABScontrol unitturns ontheABS ind icator when the unitdetectsa problem andthe unit stops th e system.
4. The self-diagnosis can be classified into these two categories:. lnitial diagnosis. Regular diagnosis
On-board Diagnosis Function
The ABS can be diagnosed with the Honda PGM Tester.
The ALB Checker cannot be used with this system. For air bleeding and checking wheel sensor signals. use the Honda
PGM Tester. See the Honda PGM Tester user's manual for specific operating instructions.
(cont'd)
T---
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ABS Components
System Description (cont'd)
ABS Modulator
The ABS modulator consists of the inlet solenoid valves, outlet solenoid valves, reservoir, pump, pump motor, and the
damping chamber. The modulator reduces the caliper fluid pressure directly. lt is a circulating-type modulator
becausethe brakefluidcirculatesthroughthecaliper,reservoir,andthemastercylinder.Thehydrauliccontrol has
three modes: pressure intensifying, pressure retaining, and pressure reducing. The hydraulic circuit is an independent
four-channeltype, one channel for each wheel.
Pressure intensifying mode: Inletvalve open, outlel valve closed
Master cylinder fluid is pumped out to the caliper.
Pressure retaining mode: lnlet valve closed, outlet valve closed
Caliper fluid is retained by the inlet valve and outlet valve.
Pressure reducing mode: Inlet valve closed, outlet valve open
Caliper fluid flows through the outlet valve to the reservoir.
lvlotor operation mode: When starting the pressure reducing mode, the pump motor is ON.
When stopping ABS operation, the pump motor is OFF.
The caliper fluid is pumped out by the pump, through the damping chamber, to the
master cvlinder.
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t
Wheel Sensors
The wheel sensors are the magnetic contactless type. As the gear pulser teeth rotate past the wheel sensor's magnetic
coil, AC current is generated. The AC frequency changes in accordance with the wheel speed. The ABS control unit
detects the wheel sensor signal frequency and thereby detects the wheel speed.
!t LOW SPEED
Wheel Speed and Modulator Control
8E!EEETqE VEJ!q!ESPEEq
5
PRESSURE
OUTLETVALVE 9p
OFF
INLETVALVE oN
OFF
MoroR I-,. ltlOFF
When the wheel speed drops sharply below the vehicle speed, the inlet valve closes and il necessary, the outlet valve
opens momentarily to reduce the caliper fluid pressure. The pump motor starts at this time. As the wheel speed is
restored, and the outlet valve closes, the inlet valve opens momentarily to increase the caliper fluid pressure.
GEAR PULSERWHEEL S€NSOR.r HIGX SPEED
19-41

ABS Components
q,
CONNECTOR A {12P)BRAKE PEDAL POSITIONSWITCH 4P CONNECTOR
Circuit Diagram (cont'd)
UNDER-HOOD FUSE/RELAY BOX CONNECTORSCONNECTOR A {12P) CONNECTOR B {2P}
UNDER.DASH FUSE/RELAY BOX CONNECTORSCONNECTOR I {5P)CONNECTOR K I17P)MULTIPLEX CONTROLUNIT 13P CONNECTOR
CONNECTOR B I22PI
1l2l3l,/15
GAUGE ASSEMBLY CONNECTORS
CONNECTOR A I22P)
WHEEL SENSOR 2P CONNECTORS
FRONT
J --T:-l Ltqtt/)l'l L_.:-:J r\-r-----Tr'e:l
RIGHT.REAR LEFT-REAR
tslTt?t /J 1T-1\I tL | rlziJ
Terminal side of male lerminals
ABS CONTROL UNIT 3IP CONNECTOR
OATA LINK CONNECTOR {16P)
Terminal side of female terminals
Wire side of female terminals
1234567
810111213141511
123,/ ,/
67891011n213
1245678I11121415
161118192021/1,/1,/vl,/l
/t,/t/t,/t/
19-44

\
DTC Troubleshooting
DTC 11, 13, 15, 17: Wheel Sensor
(Open/Short to Body Ground/Short to Power)
1. Disconnect the ABS control unit 31P connector.
2. Sta rt the engine.
3. Measure the voltage between the appropriate
wheel sensor (*)circuitterminal of theABS
control unit 31P connector and body ground (see
table).
DTCADpropriate Terminal
11 (Rioht-front)No.5: FRS (t)
13 (Left-front)No, 7: FLS (*)
15 {Riqht-rear}No. 2: RRS (*)
17 (Left-rear)No.9 RtS (f )
ABS CONTROL UNIT 31P CONNECTOR
FRS {+IIGNR/BLK} FLS I+I (BLU
RRS {+)(GNR/YEL)
Wire side of female terminals
ls thete battery voltage?
YES Repair short to power in the (+) circuit wire
between the ABS modulator-control unit and the
appropriate wheel sensor. I
NO Go to step 4.
4. Turn the ignition switch OFF.
5. Check for continuity between the appropriate
wheel sensor (+ ) circuit terminal and body ground
{see table).
DTCAppropriate Terminal
11 (Riqht-front)No. 5: FRS (+)
13 (Left-front)No. 7: FLS (*)
15 (Rioht-rear)No.2: RRS (*)
17 (Left-rear)No.9 RLS (+l
ABS CONTROL UNIT 31P CONNECTOR
Wire side
ls there continuity?
YES Go to step 6.
NO-Go to step 7.
Disconnect the harness 2P connector from the
appropriate wheel sensor, then check for continuity
between the 1+)and ( )terminals ofthe harness
and body ground.
ls there continuity?
YES-Repair shortto body ground in the (+)or { )
circuit wire between the ABS modulator-control
unit and the wheel sensor.l
NO Repiace the wheel sensor.l
(cont'd)
Wire side of female terminals
19-45

ABS Components
DTC Troubleshooting (cont'dl
7. Check the resistance between the appropriate
wheel sensor (+) and ( ) circuit terminals {seeta ble).
DTCAppropriate Terminal
l+) Side*lSide
11 {Riqht-front)No.5: FRS (*)No.4:FRS 1-)'13 {Left-front)No. 7: FLS {+iNo.6: FLS (-
15 (Rioht-rear)No. 2: RBS {+)No. 1:RBS (-)
17 (Left-rear)No.9: RLS 1-No.8: BLS (-
ABS CONTROL UNIT 31P CONNECTOR
Wire side of female terminals
Is the rcsistance between 450 2,000 A ?
YES Check for a loose ABS control unit3lP
connector. lf necessary. substitute a known-good
ABS modulator-control unit, and recheck.l
NO Go to step 8.
Disconnect the harness 2P connector from theappropriate wheel sensor, and check the resistance
between the (+) and { )terminalsof thewheel
sensor.
ls the resistance between 450- 2,000 Q ?
YES-Repair open in the (+) or (-) circuit wire, orshort between the (+) circuit wire and the { )circuit wire between the ABS modulator-control
unit and the wheel sensor.l
NO Replace the wheel sensor.l
19-46
DTC12,14, 16, 18: Wheel Sensor Putse
Signal
NOTE: lf the ABS indicator comes on for the reasonsdescribed below, the indicator goes off when you test-drive the vehicle at 31 mph (50 km/nl.
. Only the drive wheel rotated. The vehicle spun. Electrical noise
1. Visually check for appropriate wheel sensorandpulser installation and condition (see table).
DTCAppropriate Wheel Sensor
12Riqht-front
14Left-front
Riqht-rear
18Left-rear
Ate they installed correctly and not damaged?
YES-Go to step 2,
NO Reinstall or replace the appropriate wheelsensor or pulser,I
Disconnect the ABS control unit 31P connector.
Measure the resistance between the appropriate
wheel sensor ( f) and ( ) circuit terminals (see
table).
ls therc less than 450 Q ?
YES Go to step 1.
NO-Go to step 4.
\\|D
2.
3.
DTCAppropriate Terminal
l*) Side) Side
12 {Rioht-front)No.5:FBS (*No.4:FBS
14 (Left-front)No.7;FLS l*No,6:FLS
16 (Riqht.rear)No.2: RRS (*No. 1:BRS
18 (Left-readNo.9: BLS 1-No.8:RLS

4. Check for continuity between the appropriate
wheel sensor (+) circuittermlnal and otherwheel
sensor (+) circuit terminals (see table).
DTCAppropiate
Terminal
Other Terminal
12No.5:
FRW (*i
No.7No.2No.9
'14No.7:
FLW IT.)
No.5No.2No.9
toNo.2;
RRW (T-)
No.5No.7No.9
18No.9:
RLW (*)No.5No. 7No.2
ls there continuity?
YES Repair short in the wires between the
appropriate wheel sensor and the other wheel
sensor harnesses.l
NO Clear the DTC, disconnect the Honda PGM
Tester, and test-drive the vehicle. lf the ABS
indicator comes on and the same DTC is indicated,
replace the ABS modulator-control unit.l
Disconnect the harness 2P connector from the
appropriate wheel sensor and check the resistance
between the (+) side and the (-) side ofthe wheel
sensor.
ls there less than 450 Q ?
YES Replace the wheel sensor.
NO- Repair short to wire between the appropriate
wheel sensor (+) and (-)circuits.l
DTC 21: Continuous Operation (Chipped
pulser)
1. Clear the DTC, then disconnect the Honda PGM
tesler.
2. Test-drive the vehicle at 19 mph (30 km/h) or more.
Doesthe ABS indicator come on and is DTC 21
ind icated?
YES Go to step 3.
NO The system is OK at this time.l
3. Check the pulser gear for a chipped tooth.
ls the pulser OK?
YES Check for a loose ABS control unit 31P
connector. lf necessary, substitute a known-good
ABS modulator-control unit, and recheck.l
NO Replace the driveshaft or hub unit (chipped
pulser gear).1
1g-47

ABS Gomponents
ABS Modulator-Control Unit Removal and Installation {cont'dl
3. Disconnectthe six brake lines.
4. Remove the two I mm nuts.
5. Remove the ABS modulator-control unit (C).
Installation
'1. InstalltheABS modulatorcontrol unit, then tighten the two 8 mm nuts.
2. Align the connecting surface ofthe ABS control unit 3'lP connector.
3. PushinthelockoftheABScontrol unit 31P connector until you hear it click into place. then connect the connector.
4. Connect the six brake Iines.
5. Bleed the brake system, starting with the front wheels.
6. Connect the PGM Tester, and do the solenoid function test for each wheel.
7. Bleed the brake system again, staning with the front wheels.
8. Start the engine, and check that the ABS indicator and brake system indicator go off.
9. Disconnect the Honda PGM Tester. Test-drive the vehicle, and check that the ABS indicator and brake qvqtem
indicator do not come on.
19-58