Anti-lock Brake System (ABS)
Features/Construction
When the brake pedal is pressed during driving, the wheels can lock before the vehicle comes to a stop. In such an event,
the maneuverability of the vehicle is reduced if the front wheels are locked, and the stability of the vehicle is reduced if the
rear wheels are locked, creating an extremely unstable condition. The ABS precisely controls the slip rate of the wheels to
ensure maximum grip force from the tires, and it thereby ensures maneuverbility and stability of the vehicle.
The ABS calculates the slip rate of the wheels based on the vehicle speed and the wheel speed, then it controls the brake
fluid pressure to attain the target slip rate.
Grip Force of Tire and Road Surlace
COEFFICIENT OFFRICTION
TARGET SLIP RATE
RADIALOIRECTIONOF THEROTATIONALDIRECTION
SLIP RATE
19-24
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ABS 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 it 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 intensi{ying modes.
Self-diagnosis Function
The ABS control unit is equipped with a main cPU and a sub cPU, that check each other for problems.
The CPUs check the circuit of the system.
When the CPUS detect failure, they shift to the "system down mode" or the "control inhibition mode".
The self-diagnosis can be classitied into these four categories:
O: Initial diagnosis
O: Except ABS control
O; During ABS control
@: During warning
On-board Diagnosis Function
The ABS system 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
PGIM Tester. See the Honda PGM Tester user's manuals for specific operating instructions.
(cont'd)
19-29
ABS CONTROL I-INIT
MODEABSINDICATOR LIGHTMAIN
RE LAY
SOLENOID
VALVERestan conditionDTC
SYSTEM
DOWNONNo
operatron
Drive
inhibitionOperation*rlgnition
switchOFF - oN (ll)Memory
CONTROL
INHIBITIONONNo
operaton
Drive
inhibitionOperationAutomaticlVemory
*1: Except CPU failure
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Wheel Sensor
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
at LOW SPEED
wheel Sp€od and Modulatot Control
VEHICLE SPEED
VEHICLE SPEED
WHEEL SPEED
PRESSU
OUTLETVALVE ON
OFF
INLETVALVE ON
OFF
MOTOR
ON
OFF
When the wheel speed drops sharply below the vehicle speed, the outlet valve opens momentarily to reduce the caliper
fluid pressure. The pump motor starts at this time. As the wheel speed is restored. the inlet valve opens momentarily to
increase the caliDer fluid oressure.
F
GEAR PULSER
19-31
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Troubleshooting Precautions
ABS lndicalor
1 lf the system is oK, the ABS indicator goes off two seconds after turning the ignition switch oN 1l) wathout staningthe engine, and then comes on again and goes off after two seconds. This occurs because the ABS control unit isturned on by the lG2 power source.2. The ABS indicator comes on when the ABS control unit detects a problem in the system. However, even thouoh thesystem is operating properly, the ABs indicator will come on too, under the following conditions:. Signal disturbance
. Wheel spin
. Only drive wheels rotate. Battery voltage fluctuates
To determine the actual cause of the problem, question the customer about the problem, taking these conditions intoconsideration:
3 When a problem is detected and the ABS indicator comes on, the indicator can stay on until the ignition switch isturned OFF, or it can automatically go off, depending on the mode.. Indicator stays on untilthe ignition switch is turned off: When the system is in the system down mode.. Indicator automatically goes off: When the system is in the control inhibition mode.4 The ABS indicator stays on when the system is reactivated without erasing the DTC, but it goes off after starting thevehicle.
When the wheel sensor system is faulty and the ABS indicator comes on. the algorithm of the system automatically turnsoff the ABS indicator after the wheel speed signal returns to the normal speed. Also, when the DTc is erased, the cpu isreset and the ABS indicator goes off when the system checked out normal by the initial diagnosis.Therefore, test-drive the vehicle after servicing the wheel sensor system. and be sure that the ABS indicator does notcome on.
5 When the ABS control unit outputs battery voltage to the gauge assembly, the ABS indicator ooes off.
Diagnostic Trouble Code (DTCI
1. The diagnostic trouble code (DTc) is memorized when a problem is detected and the ABS indicator does not go off,or when the ABS indicator comes on.The DTc is not memorized when the ABS indicator comes on unress the cpu is activated,2 The memory can hold any number of DTCs. However, when the same DTc is detected twice or more, the tater one iswritten over the old one.
Therefore, when the same problem is detected repeatedly, it is recorded as one DTC.3. The DTCs are indicated in the order of ascending number, not in the order they occur.4. The DTCS are memorized in the EEPROM (non-volatile memorv).Therefore, the memorized DTcs cannot be canceled by disconnecting the battery. perform the specified procedures toerase the DTCS.
Self-diagnosis
1. Self-diagnosis can be classified into these four categories:' Initial diagnosis: Performed right after the eng ine starts and untir theABS indicator goes off.. Except ABS control: Performed when the ABS is not functioning.. During ABS control: Performed when the ABS is functioning.. During warning: Performed when the ABS indicator is ON.2. The system performs the fo|owing contrors when a probrem is detected by the serf-diagnosis:. ABS indicator ON. Memorv of DTC. Mode changetothe "system down mode,, or the ,,control inhibition mode,,.
MODEABS INDICATORMAIN
RELAY
SOLENOID
VALVECPURestart conditionDTC
SYSTEM
DOWNONNo
operation
Drive
inhibitionOperation*rlgnition
switchoFF - ON l)Memory
CONTROL
INHIBITIONONNo
operal|on
Drive
inhibitionOperationAutomaticlMemory
*1: Except CPU failure
19-36
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Kickback'1. The motor operates when the ABS is functioning. and the fluid in the reservoir is forced out to the master cylinder,
causing kickback at the brake pedal.
2. The ABS control unit operates the solenoid valve when the brake pedal is released after the initial diagnosis You may
hear the solenoid valve operate at this time, but it is normal
Pumo Motol
1. The pump motor operates when the ABS is functioning
2. The ABS control unit checks the pump motor operation during acceleration. You may hear the motor operate at this
time, but it is normal.
Brake Fluid Replacement/Ail Bleeding
L Brake fluid replacement and air bleeding procedures are the same as for vehicles without ABS To ease bleeding, start
with the front wheels.
Troubleshooting
1. The troubleshooting flowchart procedures assume that the cause of the problem is still present and the ABS indicator
is still on. Following the flowchart when the ABS indicator does not come on can result in incorrect diagnosis.
2. Ouestion the customer about the conditions when the problem occurred, and try to reproduce the same conditions
for troubleshooting.
Self-diagnosis is made at various times such as the initial diagnosis, except ABS control, during ABS control, during
acceleration, during the specified vehicle speed, etc. Therefore, the symptom canngt be checked unless the check
conditions match with the problem conditjons
3. When the ABS jndicator does not come on during the test-drive. but troubleshooting is performed based on the DTC,
check lor loose connectors, poor contact of the terminals, etc., before you start troubleshooting.
4. After troubleshooting, erase the DTC and test-drive the vehicle. Be sure the ABS indicator does not come on.
5. The connector illustratjons show the female terminals with a single outline and the male terminals with a double out-
l ne.
ABS Function Test
To simulate ABS operation and activate the solenoid valves and pump, use the Honda PGM Tester.
Connect the PGM Tester to the 16P Data Link Connector (DLC). When the System Select menu is displayed, select the ABS
Test Mode menu, and follow the tester's prompts.
19-37
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- With ths ignition switch ONllll, the ABS indicatol doesnot go ott.- Atte. driving, the ABS indica-lot comas on.- With the SCS service connec-tor connocted (s€€ page 19.381,DTGr 11 - 18 sre indbated.
Check the whcol sensor circuit:1. Disconnect the ABS controlunit 26P connector.2, Nleasure the resistancebetween the appropriate wheelsensor l0) and 1'l) circuit termi-nals {see table).
. Ropair op€n in th. {01 o. lll cir-cuit wire, oa short to the (01 cir-cuit wire in the lll circuit wirobetweon the ABS control unitand th. appropriate whasl sen-sot.. Roplace the rpp.opriatc whe6lSensor.
ls the resistance OK?
/Fronr:750 - r,050 o (20"C,68"F\
\Rear: 950 -'1,450 O (20"C, 68'F,
Chock lor a short 10 power in thewheel sensoa ciacuil:1. Reconnect the ABS control unit26P connector.2. Start the engine.3. Measure the voltage betlveenthe ABS control unit 26P con-nector appropriate wheel sen-sor (0) circuit terminal andbody ground (see table).
Ropair lhort to pow.r in the l0lot 11) circuit wiro between theABS control unit and the appro-priate whool sen6or.
ls there 4 V or more?
Check for a short to body groundin the whoal s.n3or cilcuit:1. Disconnect the ABS controlunit 26P connector.2. Check lor cont;nuity betweenthe ABS control unit 26P con-nector appropriate wheel sen-sor {0) circuit terminal andbody ground {se6 table).. Ropair short to body g.ound inth6 {01 or {1} circuit wirebotweon th6 ABS cont.ol unitand tho appropriato wheol son-aot.. Roplace tho appropriate wheelsensot.
DTC 11 - 18: Wheel Sensor
NOTE: The ABS indicator comes on only when the drive wheels are turning and signal disturbance is detected, Therefore, test-drive the car at a speed of 12 mph (20 km/h) or more after turning the ignition switch from OFF to ON l), and if the ABS indica-tor does not come on, the svstem is OK.
RLl (LT BLUI FRl IGRN/BLKI
Wire side of female terminals
NOTE: Judgement value for short
NO
NOTE:. Normalvoltage: Approx. 2 V.0 V: Replace the ABS control unit.. 4 V or more indicates a shon to power.
NO(cont'dl
ABS CONTNOL UNIT 26P CONNECTOR
RROIBLU/YEL}
RRT IGRN/YELI
FLO(BRN/WHTI
FLl IGFN/ORN}
DTCAppropriate Terminal
{0}srDE(1)S|DE
11, l2lRight-front)No.8: FnoNo.21: FR1
13, 14 (Left-front)No. 10rFLoNo. 23: FLl
15, 16 (RightreadNo.4: RRoNo.17: RR1
17, l8 (Lsft-rear)No.6: RLoNo.19: RL1
(To page 19-46)
19-45
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Troubleshooting
Blower Motor Speed
Recirculation indicator light indicates Diagnostic Trouble Code (DTC) 2: A problem in the blower motor circuit
The speed of the blower motor is controlled by signals sent from the heater control panel
POWER TRANSISTOR 3P CONNECTOR
1
2)3
f
BLK
Wire side of female terminals
JUMPERWIRE
HEATER CONIROL PANEL 2OP CONNECTORWire side oI fgmale t€rminals
12,/1,/68I10
't112131ia't51611181920
LI GRN/BLK
o
LT GBN/BLK
Blower motol only runs on highspood position; h does not run inany othe. speod positions.
Self-diagnosis circuit check indi-cates a problem in the blowermotor circuit,
Chack lor.n open in the wire:1. Disconnect the power transis-tor 3P connector.2. Check for continuity betweenthe No.3 terminal and bodygro(1nd.
Chock for.n op.n in thc wirobotween ihe powa. transistorrnd body ground, It tho wir. is
OK, check for poor ground atG,O1 .nd G4o2.
ls there continuity?
Chsck for an opon in the wire:'1. Connect the No. 1 and No. 3t€rminals of the power tran-sistor 3P connector with ajumper ware.2. Turn the ignition switch ON {ll).
Repair op6n in the wiro betwoontho Dower transi3tol and theblowor motor.
Check tor an open in tho wire:1. Turn the ignition switch OFF.2. Disconnect the iumper wire.3. Remove the heater controlpanel (see page 22-46).4. Check for continuity botweenthe No. 20 terminal of theheater control panel 20P con-nector and the No.2 terminalof the power transistor 3Pconnectof,
R€pair opon in tho wire betwoenth6 oowor ttan3i3tor and th6hoatar control oanel.
NOTE: lf the blower motor doesrun at all, refer to page 22-16.
10 page 22-15
22-14
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Troubleshooting
Blower Motor
Recirculation indicator light indicates Diagnostic Trouble Code (DTC) 2: A problem in the blower motor circuit.
The speed of the blower motor is controlled by signals sent from the heater control panel,
BLOWER MOTOR 2P CONNECTOR
JUMPEFw|RE
Wire side of lemale terminals
Blower motor do.3 not run at all.
Selt-diagnosis circuit check indi-cates a problem in the blowermotor circuit,
check rhe No. 55 (40 A) {use inthe under-hood fuse/relay box,and the No. 17 (7.5 A) fuse in theunder-dash fuse/relay box.
Replace th6 fuse(s), and rechalck.
Check tho blowe. motor inputand output cilcuh:1. Connect the No. 2 terminal ofthe blower motor 2P connec-tor to body ground with ajumper wrre.2. Turn the ignition switch ON (ll).
Does the blower motor run?
Chock the blower moto.:1. Disconnect the jumper wireand the blower motor 2P con-nector.2. Measure the voltage betweenthe No. l terminal and bodygrou nd.
Check tho blower motor rolay:1. Turn the ignition switch OFF.2. Romove the blower motorrelay from the under-hoodfuse/relay box, and test it (seepage 22 45l'.
fo page 22-11
fo page 22-19
22-16
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