Brake Booster Pump Motor Malfunction
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Brake Booster Pump Motor Malfunction
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Circuit/System Description
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The electronic brake control module (EBCM) monitors the control circuit of the brake booster pump relay. The EBCM supplies ground through the pump relay control circuit which then supplies B+ voltage to actuate the brake booster pump. B+ voltage is supplied at all times to the coil side of the pump relay.
Schematic Reference
Hydraulic Brake Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Brake Assist System Description and Operation
Electrical Information Reference
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Circuit/System Verification
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2.
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Ignition ON, command the relay ON and OFF with a scan tool. Observe to verify that the vacuum relay and motor turns ON and OFF with each command.
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1.
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Ignition OFF, disconnect the vacuum pump relay.
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2.
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Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 and ground.
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3.
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If the test lamp illuminates, test the control circuit for a short to voltage.
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4.
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Verify that a test lamp illuminates between the B+ circuit terminals listed below and ground.
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If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test or replace the relay.
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5.
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Verify that a test lamp does not illuminate between the control circuit terminal 30 and ground.
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6.
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If the test lamp illuminates, test the control circuit for a short to voltage.
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7.
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Disconnect the harness connector at the vacuum pump.
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8.
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Test for less than 2 Ω between the vacuum pump ground circuit terminal 2 and ground.
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9.
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If greater than the specified range, test the ground circuit for an open/high resistance.
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10.
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Connect the harness connector at the vacuum pump.
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11.
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Connect a 20 A fused jumper wire between the B+ circuit terminal 87 and the control circuit terminal 30. Verify the vacuum pump is activated.
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12.
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If the vacuum pump does not activate, test the control circuit for a short ground or an open/high resistance. If the circuit tests normal, test or replace the vacuum pump.
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13.
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Disconnect the X1 harness connector at the EBCM.
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14.
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Ignition OFF, test for infinite resistance between the control circuit terminal 85 and ground.
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15.
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If less than the specified value, test the control circuit for a short to ground. If the circuit tests normal, replace the EBCM.
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16.
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Test for less than 2 Ω between the control circuit terminal 85 at the relay cavity and terminal 35 at the EBCM harness connector.
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17.
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If greater than the specified range, test the control circuit for an open/high resistance.
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18.
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If all circuits test normal, replace the brake booster pump relay.
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1.
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Ignition OFF, disconnect the vacuum pump relay.
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2.
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Test for 60-180 Ω between terminals 85 and 86.
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3.
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If the resistance is not within the specified range, replace the relay.
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4.
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Test for infinite resistance between the following terminals:
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If not the specified value, replace the relay.
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5.
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Install a 30 A fused jumper wire between relay terminal 86 and B+. Install a jumper wire between relay terminal 85 and ground.
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6.
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Test for less than 2Ω between terminals 30 and 87.
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7.
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If greater than the specified range, replace the relay.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
