Modulator Unit - Honda Prelude 1993 Service Manual

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Table of Contents

Anti-lock Brake System (ABS)

Features/Construction/Operation (cont'dl

1. Sell-diagnosticFunction

Since the anti-lock brake system modulates the braking pressure when a wheel is about to lock, .egardless ol the

driver's intention, the system operation and the braking power will be impaired iJ thsre is a malfunction in th€

system. To prevent this possibility, at speeds above 6 mph (1 O km/h). the selt-diagnosis function, p.ovided in the

sub-tunction of the ABS control unit. monitors the main system functions. When an abnormality is detected, tho

ABS indicator light goes on. There is also a check mode of the self-diagnosis system itself; when the ignition switch

is tirst turned on, the ABS indicator light comes on and stays on for a Jew seconds sfter the engine starts, to signify

that the self-diagnosis system is functional.

Fail-safe Function

When abnormality is detected in the control system by the self-diagnosis, the solenoid operations are suspended by

turning oft the relays Itail-sate relays) which disconnect the ground lines of all the solenoid valves to inhibit anti-lock

brake svstem operations, Under these conditions, the braking system functions just as an ordinary one, msintaining

the necessary braking function. When the ABS indicator light is turned on, it means the tail-safe is Junctioning.

Modulator Unit

Modulators for each wheel and solenoid valves are integrated in the modulator unit.

The modulators for front and rear brakes are ot independent construction and are positioned vertically for improved main-

tainability. The modulators for rear brakes are provided with a PCV function (Proportioning Control Valve) in ordel to pre-

vent the rear wheel from locking when the anti-lock brake system is malfunctioning or the anti-lock brake system is not

The solenoid valve features quick response (5 ms or less).

The inlet and outlet valves are integrated in the solenoid valve unit. There are three solenoid valves provided, on€ fol

each front wheel, and one for the rear wheels.

Prlrnary Plrto|r

To Lcft-f.ont

Brakc Cdllpol

To Rlght-rea.

B]rk. Callp€r

Troubleshooting