ABS Description. Chevrolet Prizm 1998

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1998 🢒 Prizm 🢒 Brakes 🢒 Antilock Brake System 🢒 ABS Description

This vehicle is equipped with the Lucas/Sumitomo hybrid non-integral Antilock Brake System (ABS). The system employs a single valve per channel, 4-channel system to reduce the tendency of any wheel to lock-up. This improves driver control of the vehicle during braking. The purpose of the ABS is to minimize wheel lockup during heavy braking on most road surfaces. The ABS performs this function by monitoring the speed of each wheel and the ABS performs this function by controlling the brake fluid pressure to each wheel independently during a braking maneuver. This allows the driver to retain directional stability and allows the driver better steering capability.

The purpose of the Antilock Brake System (ABS) is to minimize wheel slipping during braking, thus improving vehicle stability and steerability. The ABS accomplishes this objective by controlling the hydraulic pressure applied at each front wheel brake and both rear wheel brakes as a pair.

The ABS operation is available from approximately 6.3 km/h (4 mph) to the maximum vehicle speed. During braking the ABS is available from the maximum vehicle speed to 5 km/h (3 mph).

Electronic Brake Control Module (EBCM)/Brake Pressure Modulator Valve (BPMV) Assembly


(1)	Master Cylinder
(2)	BPMV Wiring Harness Connector
(3)	EBCM/BPMV Assembly
(4)	EBCM/BPMV Mounting Bracket
(5)	Brake Vacuum Booster

The heart of the Antilock Brake System (ABS) system is the brake pressure modulator valve assembly. It is a compact integrated unit that contains the following components:

•	An Electronic Brake Control Module (EBCM)

•	Four solenoids valves (one for each wheel brake hydraulic channel

•	Four flow control valves in-series with each wheel brake hydraulic channel (one for each solenoid valve)

•	Buffer chambers

•	A pump motor

•	Check valves

The brake pressure modulator valve assembly is located on the left rear corner of the engine compartment just below the master cylinder. The brake pressure modulator valve assembly is mounted on a bracket.

The controlling element of the Antilock Brake System (ABS) is a microprocessor based Electronic Brake Control Module (EBCM). The inputs to the system include the following components:

•	The four wheel speed sensors

•	The stoplamp switch

•	The ignition switch

•	The battery voltage

•	The OBD2 Data Link Connector (DLC)

The outputs include the following components:

•	The four solenoid valves

•	The pump motor

•	The ABS warning indicator

•

The DLC

The EBCM monitors the speed of each wheel. If any wheel tends to stop during braking the EBCM actuates solenoid valves and the pump motor to modulate hydraulic pressure to the wheel brake(s) approaching wheel slip. Once the wheel regains traction the hydraulic pressure is increased until the wheel again begins to slip. This cycle repeats until either of the following cases:

•	The vehicle comes to a stop

•	The brake pedal is released

•	No wheels approach slippage

Additionally the EBCM monitors each input and each output for proper operation. The EBCM sets a Diagnostic Trouble Code (DTC) when detecting a system malfunction. The DTC will not erase if the battery is disconnected because the EBCM stores DTCs in nonvolatile memory. Refer to Self-Diagnostics in this section for more detailed information. The EBCM is an integral part of the Brake Pressure Modulator Valve (BPMV) assembly and is not serviceable separately.

Front Wheel Speed Sensors and Rings


(1)	Front Wheel Speed Sensor
(2)	Front Wheel Speed Sensor Ring

The front wheel speed sensors are of a variable reluctance type. Each sensor is attached to the knuckle assembly in close proximity to a toothed ring. The toothed ring is pressed onto the outer Constant Velocity (CV) joint. As the toothed ring rotates the wheel speed sensor generates an AC voltage. The magnitude and the frequency are proportional to the speed of the wheel and both will increase with increasing speed. The sensor is not repairable nor is the air gap adjustable.

Rear Wheel Speed Sensors and Rings


(1)	Rear Wheel Speed Sensor
(2)	O-Ring
(3)	Brake Drum
(4)	Rear Hub and Bearing Assembly

The rear wheel speed sensors operate in the same manner as the front wheel speed sensors. The rear wheel speed sensors are mounted in the rear suspension knuckles. The rear wheel speed sensor reluctor ring is part of the rear hub and the bearing assembly. Replace the rear hub and the bearing assembly when the rear wheel speed sensor ring is damaged.

Wheel Speed Sensor Pigtail Harness

Each wheel speed sensor has a pigtail harness made up of a highly flexible twisted pair wiring. Any repair to pigtail harness will result in stiffening and eventual failure due to wire fatigue. For this reason the wheel speed sensor pigtail harness is not repairable and the wheel speed sensor must be replaced. Do not attempt to solder, splice or crimp the wheel speed sensor pigtail harness, as eventual failure will result.

Wiring Harness

The wiring harness is the mechanism by which the brake pressure modulator value assembly is electrically connected to the following components:

•	The power and ground circuits

•	The wheel speed sensors

•

The fuses

•	The switches

•	The ABS Indicator

•	The Data Link Connector (DLC)

The components considered part of the wiring harness are the wires that provide electrical interconnection and the connectors and/or terminals that provide an electrical and/or mechanical interface from the wire to a component.

ABS Indicator

The ABS indicator turns ON light to alert the driver of a malfunction. When the ABS warning indicator remains ON after the 3 second bulb check the ABS is disabled but normal (non-antilock) braking will remain. Refer to Diagnosis in this section for more information on how to pinpoint the malfunction and to regain ABS braking ability.

Fuses

The Antilock Brake System (ABS) power distribution system consists of fuses and the ignition switch. The fuses consist of the following:

•	The ABS fuse (50A) at the fuse and the relay box

•	The STOP fuse (15A)

•	The GAUGE fuse (15A) at the junction block

The fuse and the relay box is located on the left front hand of the engine compartment left of the air cleaner. The junction block 1 is located on the lower left hand shroud behind the kick panel.