Chevrolet Trax: Symptoms - hydraulic brakes

NOTE: The following steps must be completed before using the symptom tables.

1. Perform the Brake System Vehicle Road Test before using the hydraulic brake symptom tables in order to duplicate the customers concern.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to the following:

• Brake Warning System Description and Operation
• Hydraulic Brake System Description and Operation
• Brake Booster Vacuum Assist Description and Operation
• Brake Assist System Description and Operation
• ABS Description and Operation

Visual/Physical Inspection

• Inspect for aftermarket devices which could affect the operation of the hydraulic brake system. Refer to Checking Aftermarket Accessories .
• Inspect the easily accessible or visible system components, for obvious damage or conditions, which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

• Brake Booster Pump Motor Malfunction (Without J41), Brake Booster Pump Motor Malfunction (With J41)
• Brake Warning Indicator Malfunction (Without J41), Brake Warning Indicator Malfunction (With J41)
• Brake Pulsation
• Brake System Noise
• Braking Action Uneven - Pulls to One Side
• Braking Action Uneven - Front to Rear
• Brake Pedal Excessive Travel
• Brake Pedal Excessive Effort
• Brakes Drag
• Brake System Slow Release
• Brake Fluid Loss

BRAKE BOOSTER PUMP MOTOR MALFUNCTION (WITHOUT J41)

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

Circuit/System Description

The brake booster vacuum sensor measures the vacuum in the brake booster. The electronic brake control module supplies a 5 v reference and a low reference circuit to the brake booster vacuum sensor. The vacuum sensor supplies a voltage signal in relation to the pressure in the brake booster to the electronic brake control module. When the vacuum within the system becomes low, the electronic brake control module turns on the brake booster pump motor by providing battery voltage to the brake booster pump motor relay. The relay activates and supplies the voltage to the brake booster pump motor.

Reference Information

Schematic Reference

Hydraulic Brake Schematics (Encore), Hydraulic Brake Schematics (Trax)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

Description and Operation

Brake Booster Vacuum Assist 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

Circuit/System Verification

1. Ignition ON.
2. Verify the M9 Brake Booster Pump Motor turns ON and OFF when commanding the Brake Booster Electric Vacuum Pump ON and OFF with a scan tool.

If the M9 Brake Booster Pump Motor does not turn ON and OFF

Refer to Circuit/System Testing.

If the M9 Brake Booster Pump Motor turn ON and OFF

3. Verify that the brake booster vacuum system has no damage, leakage or incorrect installation.

If damage, leakage or incorrect installation is found

Refer to Brake Assist System Diagnosis.

If the inspection is OK

4. All OK.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the KR14 Brake Booster Pump Motor Relay. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 ohms between the ground circuit terminal 1 (86) and ground.

If 10 ohms or greater

1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.

If less than 10 ohms

3. Ignition ON.
4. Verify a test lamp illuminates between the B+ circuit terminal 3 (30) and ground.

If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF.
2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.

If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance

3. Test for infinite resistance between the control circuit terminal 5 (87) and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the KR14 Brake Booster Pump Motor Relay.

If the test lamp illuminates

5. Connect a test lamp between the control circuit terminal 2 (85) and the ground circuit terminal 1 (86).
6. Verify the test lamp turns ON and OFF when commanding the Brake Booster Electric Vacuum Pump ON and OFF with a scan tool.

If the test lamp is always OFF

1. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module.
2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K17 Electronic Brake Control Module.

If the test lamp is always ON

1. Ignition OFF, disconnect the harness connector at the K17 Electronic Brake Control Module, ignition ON.
2. Test for less than 1 V between the control circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K17 Electronic Brake Control Module.

If the test lamp turns ON and OFF

7. Verify that a test lamp does not illuminate between the control circuit terminal 5 (87) and ground.

If the test lamp illuminates

Repair the short to voltage on the control circuit

If the test lamp does not illuminate

8. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the M9 Brake Booster Pump Motor. It may take up to 2 min for all vehicle systems to power down.
9. Test for less than 10 ohms between the M9 Brake Booster Pump Motor ground circuit terminal 2 and ground.

If 10 ohms or greater

1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.

If less than 10 ohms

10. Connect the harness connector at the M9 Brake Booster Pump Motor.
11. Ignition ON, connect a 30 A fused jumper wire between the B+ circuit terminal 3 (30) and the control circuit terminal 5 (87).
12. Verify the M9 Brake Booster Pump Motor is activated.

If the M9 Brake Booster Pump Motor does not activate

1. Ignition OFF, disconnect the harness connector at the M9 Brake Booster Pump Motor.
2. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the M9 Brake Booster Pump Motor.

If the M9 Brake Booster Pump Motor activates

13. Test or replace the KR14 Brake Booster Pump Motor Relay.

Component Testing

Motor Test

1. Ignition OFF, disconnect the harness connector at the M9 Brake Booster Pump Motor. Install a 30 A fused jumper wire between the B+ circuit terminal 1 and B+. Install a jumper wire between the ground circuit terminal 2 and ground.
2. Verify the M9 Brake Booster Pump Motor activates.

If the brake booster pump motor does not activate

Replace the M9 Brake Booster Pump Motor.

If the brake booster pump motor activates

3. All OK.

Relay Test

1. Ignition OFF, disconnect the KR14 Brake Booster Pump Motor Relay.
2. Test for 60-180 ohms between terminals 1 and 2.

If less than 60 or greater than 180 ohms

Replace the relay.

If between 60-180 ohms

3. Test for infinite resistance between the terminals listed below:

• 30 and 86
• 30 and 85
• 30 and 87
• 85 and 87

• If less than infinite resistance

Replace the relay.

If infinite resistance

4. Install a 20 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground.
5. Test for less than 2 ohms between terminals 30 and 87.

If 2 ohms or greater

Replace the relay.

If less than 2 ohms

6. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Relay Replacement (Within an Electrical Center) , Relay Replacement (Attached to Wire Harness) .
• Power Brake Booster Pump Replacement .
• Control Module References for Electronic Brake Control Module replacement, programming and setup.

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