Mitsubishi Eclipse 1990-1998 Repair Guide

General Information

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Both FWD and AWD systems monitor and compare wheel speed based on the inputs from the wheel speed sensors. The brake pressure is controlled according to the impending lock-up computations of the ABS control unit.

On the FWD vehicles using a 3-channel system, if either front wheel approaches lock-up, the controller actuates the individual solenoid for that wheel, reducing pressure in the line. Impending lock-up at either rear wheel will engage the rear control solenoid; hydraulic pressure is reduced equally to both rear wheels, reducing the tendency of the rear to skid sideways under braking.

The AWD vehicles incorporate a G-sensor into the system to give the ABS control unit an acceleration signal; this is used in conjunction with engine rpm and wheel speed signals to determine high or low friction road conditions. If the system detects impending wheel lock at, for example, the left front wheel, the solenoid controlling the left front/right rear circuit is activated to reduce line pressures. The select-low valve (common to both channels) reacts to the pressure change and reduces the pressure to the other rear wheel. This system overcomes some of the inherent problems of applying ABS to all wheel drive vehicles.

The system incorporates an idle-up control which raises engine speed to 1800 rpm during braking. This eliminates engine braking during ABS-engaged stops and allows the control system to apply maximum stopping effort.

Also found on the AWD is a delay valve which prevents simultaneous front and rear wheel slip by momentarily delaying rear wheel cylinder pressure when ever front wheel line pressure increases sharply. This insures more even application of braking force to the ground and better vehicle control for the operator.

Three separate relays aid the operation of the ABS system. The ABS motor relay (for the pump motor) and the ABS valve relay are located together immediately adjacent to the hydraulic unit under the hood.

The ABS power relay is mounted on a separate bracket next to the anti-lock control unit in the right rear quarter panel. Each of the relays may be replaced in the usual fashion, although care must be taken to release wiring connector clips before removing the relay.

FLAT BATTERY REMEDY



When booster cables are used to start the engine when the battery is completely flat and the vehicle is immediately driven without waiting for the battery to recharge itself, the engine may misfire, and driving may not be possible. This is due to the fact that the ABS consumes a great amount of current for it self-check functions; the remedy is to either allow the battery to recharge sufficiently, or to disconnect the electrical harness connector for the ABS circuit, thus disabling the ABS system. The ABS warning light will illuminate when the connector is disconnected.

After the battery has been sufficiently charged, engage the ABS electrical connector and restart the engine. Check to be sure the ABS warning lamp is not illuminated.

SYSTEM PRECAUTIONS





Certain components within the ABS system are not intended to be serviced or repaired individually. Only those components with removal and installation procedures should be serviced.
 
Do not use rubber hoses or other parts not specifically specified for the ABS system. When using repair kits, replace all parts included in the kit. Partial or incorrect repair may lead to functional problems and require the replacement of components.
 
Lubricate rubber parts with clean, fresh brake fluid to ease assembly. Do not use lubricated shop air to clean parts; damage to rubber components may result.
 
Use only DOT 3 brake fluid from an unopened container.
 
If any hydraulic component or line is removed or replaced, it may be necessary to bleed the entire system.
 
A clean repair area is essential. Always clean the reservoir and cap thoroughly before removing the cap. The slightest amount of dirt in the fluid may plug an orifice and impair the system function. Perform repairs after components have been thoroughly cleaned; use only denatured alcohol to clean components. Do not allow ABS components to come into contact with any substance containing mineral oil; this includes used shop rags.
 
The Anti-Lock control unit is a microprocessor similar to other computer units in the vehicle. Ensure that the ignition switch is OFF before removing or installing controller harnesses. Avoid static electricity discharge at or near the controller.
 
If any arc welding is to be done on the vehicle, the ALCU connectors should be disconnected before welding operations begin.
 

DEPRESSURIZING THE SYSTEM



The ABS system requires no special system depressurization prior to the opening of hydraulic lines or bleeding of the system.

 
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