LeSabre V6-181 3.0L (1986)
Electronic Brake Control Module: Description and Operation
The EBCM performs the following functions:
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Closes switched BAT circuit through the main relay when the ignition switch is in "RUN" position
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Opens switched BAT circuit through the main relay when:
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The ignition switch is in "OFF" or "crank" position
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It detects an electrical failure with itself, the wheel speed sensors, or valve solenoids
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Monitors the fluid level sensor and pressure switch input to turn ON the "ANTILOCK" warning lamp, if necessary
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Monitors the four wheel speed sensor signals, compares them, and operates the main valve and valve block solenoids, if necessary The EBCM
mounts in the passenger compartment or trunk, depending on vehicle application. Programming of the EBCM is tailored to each individual
vehicle in a specific model year, so units should not be interchanged. The EBCM uses a unique 35-pin electrical connector, which requires
careful service. EBCM operational steps:
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When the ignition switch is in the "run" position, EBCM terminal 2 receives a 12-volt "ignition enable" signal. Terminal 1 completes the circuit
path to chassis ground for EBCM circuits.
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The EBCM will conduct an electrical check of:
1.
Itself
2.
Wheel speed sensor circuits (resistance)
3.
Main valve solenoid circuit (resistance and current usage)
4.
Valve block solenoid circuits (resistance and current usage)
5.
Fluid level sensor/pressure "loop" circuit (resistance)
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If checks 1 through 4 are bad, the EBCM will not complete the main relay control winding circuit.
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If checks 1 through 4 are good, the EBCM will complete the control circuit of the main relay. This will turn OFF the "ANTILOCK" warning
lamp and send operating power to EBCM terminals 3 and 20. A diode allows terminal 27 of the EBCM to turn on the "ANTILOCK" lamp
without shorting switched BAT to ground.
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If the main relay fails to power up EBCM pins 3 and 2O, the EBCM will complete the "ANTILOCK" warning lamp circuit.
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If check 5 indicates low fluid level and/or low pressure, the EBCM energizes the main relay and completes the "ANTILOCK" warning lamp
circuit to ground at terminal 27.
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When the ignition switch is in the "crank" position, one of two things will happen to cause the EBCM to turn OFF the main relay (depending on
vehicle application):
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Ignition enable voltage at EBCM terminal 2 will drop to zero.
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The EBCM will receive a cranking voltage signal at terminal 19.
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On the Pontiac STE AWD "differential lock engaged" switch will open the "ignition enable" circuit, preventing ABS operation.
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When the wheel speed sensors send signals to the EBCM, the EBCM will check them for correct voltage and waveform. If it detects a problem,
the EBCM will turn OFF the main relay.
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If the wheel speed sensor signals check good, the EBCM will monitor them for an indication of locking during braking. On some vehicle
applications a 12-volt input signal from the brake pedal switch to terminal 12, indicates a driver brake input.
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The EBCM will continue to check its circuits while it is turned ON. If it detects a problem, the EBCM will turn OFF the main relay or operate
the "ANTILOCK" lamp circuit.
