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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 XLR 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Park Brake Will Not Hold

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Park Brake Hold Relay Control

2

2

1

--

Park Brake Hold Relay Coil Ground

--

2

--

--

  1. Park brake will not release
  2. Park brake will not hold

Circuit/System Description

The park brake system uses a pair of solenoids to set or release the park brake pedal. These solenoids are powered by relays which are commanded ON and OFF by the body control module (BCM). When the gear shift lever is taken out of Park or Neutral, the BCM simultaneously activates both solenoids to release the park brake pedal. The release solenoid remains activated until the gear shift lever is in Park or Neutral, the engine is OFF and the park brake switch is closed.

Diagnostic Aids
    •  With the park brake pedal applied, observe the red brake warning indicator, if not illuminated refer to Brake Warning Indicator Malfunction.
    •  Inspect the park brake system for proper operation. Refer to Park Brake System Diagnosis.
    •  Inspect the disc brake system for proper operation. Refer to Disc Brake System Diagnosis.
    •  Inspect the hydraulic brake system for proper operation. Refer to Hydraulic Brake System Diagnosis.

Reference Information

Schematic Reference

Park Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Park Brake System Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information.

Circuit/System Verification
    •  Ignition ON, command the Park Brake Solenoid Relay A ON and OFF with a scan tool. Feel/Listen for the park brake hold relay turning ON and OFF in the instrument panel fuse block. If the relay does not activate refer to Component Testing Park Brake Release Relay before Circuit/System Testing.
    •  Ignition ON, command the Park Brake Solenoid Relay B ON and OFF with a scan tool. Feel/Listen for the park brake release relay turning ON and OFF in the instrument panel fuse block. If the relay does not activate refer to Component Testing Park Brake Hold Relay before Circuit/System Testing.

Circuit/System Testing
  1. Ignition OFF, disconnect the Park Brake Hold Relay.
  2. Test for less than 2.0 ohms between the ground circuit terminal D1 and ground.
    3. ⇒ If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Test for less than 2.0 ohms between the ground circuit terminal D5 and ground.
    4. ⇒ If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Disconnect the harness connector at the Park Brake Pedal Assembly.
  5. Verify that a test lamp illuminates between the park brake pedal assembly B+ circuit terminal B and ground.
    6. ⇒ 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 park brake release solenoid.
  6. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal D3 and B+.
    7. ⇒ If the test lamp illuminates, test the control circuit for a short to ground.
  7. Connect the harness connector at the park brake pedal assembly.
  8. Connect a 3 A fused jumper between the ground circuit D5 and the control circuit terminal D3. Verify the park brake hold relay is activated.
    9. ⇒ If it does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the park brake release solenoid.
  9. Connect a test lamp between the control circuit terminal D2 and the ground circuit terminal D1.
  10. Command the Park Brake Solenoid Relay B ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    11. ⇒ If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒ If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  11. If all circuits test normal, test or replace the park brake hold relay.

Component Testing

Park Brake Hold Relay

  1. Ignition OFF, disconnect the Park Brake Hold Relay.
  2. Test for 0-2 ohms between terminals D2 and D1.
    3. ⇒ If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals:
    4. •  D3 and D1
    •  D3 and D5
    •  D2 and D3
    •  D2 and D5
         ⇒ If not the specified value, replace the relay.
  4. Install a 3 A fused jumper wire between relay terminal D2 and 12 volts. Install a jumper wire between relay terminal D1 and ground. Test for less than 2.0 ohms between terminals D3 and D5.
    5. ⇒ If greater than the specified range, replace the relay.

Park Brake Release Relay

  1. Ignition OFF, disconnect the Park Brake Release Relay.
  2. Test for 0-2 ohms between terminals C2 and C1.
    3. ⇒ If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals:
    4. •  C2 and C5
    •  C3 and C5
    •  C2 and C3
    •  C2 and C1
         ⇒ If not the specified value, replace the relay.
  4. Install a 3 A fused jumper wire between relay terminal C2 and 12 volts. Install a jumper wire between relay terminal C1 and ground. Test for less than 2.0 ohms between terminals C3 and C5.
    5. ⇒ If greater than the specified range, replace the relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Parking Brake Lever Pedal Assembly Replacement
    •  Park Brake Release Solenoid Replacement
    •  Relay Replacement
    •  Control Module References for BCM replacement, setup, and programming.