Reno L4-2.0L (2006)
Electronic Brake Control Module: Description and Operation
System Components Description
Electronic Brake Control Module (EBCM) Description
NOTE: There is no serviceable or removable EEPROM. The EBCM must be replaced as an assembly.
The EBCM is attached to the hydraulic unit in the engine compartment. The controlling element of ABS 5.3 is a microprocessor-based EBCM. Inputs
to the system include the four wheel speed sensors, the stoplamp switch, the ignition switch, and the unswitched battery voltage. There is an output to
a bi-directional serial data link, located in pin K of Data Link Connector (DLC) for service diagnostic tools and assembly plant testing.
The EBCM monitors the speed of each wheel. If any wheel begins to approach lockup and the brake switch is closed (brake pedal depressed), the
EBCM controls the solenoids to reduce brake pressure to the wheel approaching lockup. Once the wheel regains traction, brake pressure is increased
until the wheel again begins to approach lockup. This cycle repeats until either the vehicle comes to a stop, the brake pedal is released, or no wheels
approach lockup. Additionally, the EBCM monitors itself, each input (except the serial data link), and each output for proper operation. If it detects
any system malfunction, the EBCM will store a DTC in nonvolatile memory (EEPROM) (DTCs will not disappear if the battery is disconnected).
Refer to Self-Diagnostics for more detailed information.
Front Wheel Speed Sensor Description
The front wheel speed sensors are of a variable reluctance type. Each sensor is attached to the steering knuckle, close to a toothed ring. The result, as
teeth pass by the sensor, is an AC voltage with a frequency proportional to the speed of the wheel. The magnitude of the voltage and frequency
increase with increasing speed. The sensor is not repairable, nor is the air gap adjustable.
Front Wheel Speed Sensor Rings Description
The toothed ring mentioned above is pressed onto the wheel-side (outer) constant velocity joint. Each ring contains 47 equally spaced teeth. Exercise
care during service procedures to avoid prying or contacting this ring. Excessive contact may cause damage to one or more teeth. If the ring is
damaged, the wheel-side constant velocity joint must be replaced.
Rear Wheel Speed Sensor and Rings Description
The rear wheel speed sensors operate in the same manner as the front wheel speed sensors. They incorporate a length of flexible harness with the
connector attached to the end of the harness. The rear wheel speed rings are incorporated into the hub assemblies and cannot be replaced separately,
but require replacement of the rear hub/bearing assembly.
Value Relay and Pump Motor Relay Description
The valve relay and the motor pump relay are located inside the Electronic Brake Control Module (EBCM) and are not replaceable. If one should fail,
replace the EBCM.
Wiring Harness Description
The wiring harness is the mechanism by which the Electronic Brake Control Module (EBCM) is electrically connected to power and to ground, to the
wheel speed sensors, the fuses, the switches, the indicators, and the serial communications port. The components, considered part of the wiring
harness, are the wires that provide electrical interconnection, and connectors (terminals, pins, contacts, or lugs) that provide an electrical/mechanical
interface from the wire to a system component.
Indicators Description
The Electronic Brake Control Module (EBCM) continuously monitors itself and the other ABS components. If the EBCM detects a problem with the
system, the amber ABS indicator will light continuously to alert the driver to the problem. An illuminated ABS indicator indicates that the ABS
system has detected a problem that affects the operation of ABS. No antilock braking will be available. Normal, non-antilock brake performance will
remain. In order to regain ABS braking ability, the ABS must be serviced.
The red BRAKE indicator will be illuminated when the system detects a low brake fluid level in the master cylinder or when the parking brake switch
is closed (the parking brake is engaged) or EBD system is disabled.
NOTE: EBD indicator lamp wiring is connected to the parking brake lamp. If the parking brake lamp is turned on when you driving, checking on
whether the parking brake lever is engaged or the brake fluid level is low. If the system has no problem, the EBD system is working improperly. The
EBD system must be serviced.
