Chevrolet Silverado / GMC Sierra. Service manual — part 2360

Brake Fluid Level Indicator Switch Replacement (JD9, JF3, JF7)

Control Module References for IPC replacement, setup, and programming

SYMPTOMS - HYDRAULIC BRAKES

1. Perform the Brake System Vehicle Road Test before using the hydraulic brake symptom

tables in order to duplicate the customer's concern.

2. Review the system operation in order to familiarize yourself with the system functions.

Refer to the following procedures:

Brake Warning System Description and Operation

Hydraulic Brake System Description and Operation

Brake Assist System Description and Operation (Hydraulic Assist)Brake Assist
System Description and Operation (Vacuum Assist)

Disc Brake System 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 Warning Indicator Malfunction

Brake Pulsation

Brake System Noise

Braking Action Uneven - Pulls to One Side

IMPORTANT: The following steps must be completed before using the symptom

tables.

2008 Chevrolet Silverado 1500

2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Braking Action Uneven - Front to Rear

Brake Pedal Excessive Travel

Brake Pedal Excessive Effort

Brakes Drag

Brake System Slow Release

Brake Fluid Loss

BRAKE WARNING INDICATOR MALFUNCTION

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 instrument panel cluster (IPC) sees the brake fluid level switch input opens and illuminates
the Red Brake Warning indicator. The body control module (BCM) sees the park brake switch
input grounded, it sends a serial data message to the IPC requesting illumination of the Red Brake
Warning indicator.

Reference Information

Schematic Reference

Hydraulic Brake Schematics

Connector End View Reference

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Brake Fluid Level Signal

1

1

1

-

Park Brake Signal

1

1

1

-

Ground

-

1

-

-

1. Brake Warning Indicator Malfunction

2008 Chevrolet Silverado 1500

2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Component Connector End Views

Description and Operation

Brake Warning 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

1. Verify the park brake is released and the brake fluid is at or above the proper level.

If low, refer to Brake Fluid Loss.

2. Command the IPC display test with a scan tool, the warning indicator should turn ON.

If the red brake warning indicator does not illuminate, replace the IPC.

3. Ignition ON, observe the scan tool BCM Park Brake Switch parameter while applying and

releasing the park brake. The parameter should cycle between Applied and Release.

If the parameter does not cycle between the specified values, refer to Park Brake
Switch Malfunction below.

4. Observe the scan tool IPC Brake Fluid parameter. The reading should be OK.

If not the specified value, refer to Brake Fluid Level Switch Malfunction below.

Circuit/System Testing

Park Brake Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the park brake switch.

2. Ignition ON, verify the scan tool BCM Park Brake Switch parameter is Released.

If not the specified value, test the signal circuit terminal A for a short to ground. If the
circuit tests normal, replace the BCM.

2008 Chevrolet Silverado 1500

2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

3. Install a 3A fused jumper wire between the signal circuit terminal A and ground. Verify the

scan tool BCM Park Brake Switch parameter is Applied.

If not the specified value, test the signal circuit for a short to voltage or an open/high
resistance.

4. If all circuits test normal, test or replace the park brake switch.

Brake Fluid Level Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the brake fluid level switch.

2. Test for less than 1 ohm between the ground circuit terminal A and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool IPC Brake Fluid parameter is Ok.

If not the specified value, test the signal circuit for a short to ground. If the circuit tests
normal, replace the IPC.

4. Install a 3A fused jumper wire between the signal circuit terminal B and ground. Verify the

scan tool IPC Brake Fluid parameter is Low.

If not the specified value, test the signal circuit for a short to voltage or an open/high
resistance. If the circuit tests normal, replace the IPC.

5. If all circuits test normal, test or replace the brake fluid level switch.

Component Testing

Park Brake Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the park brake switch.

2. Test for infinite resistance between the signal terminal A and ground with the park brake

released.

If less than the specified value, replace the park brake switch.

3. Test for less than 1 ohm between the signal terminal A and ground with the park brake

applied.

If greater than the specified range, replace the park brake switch.

Brake Fluid Level Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the brake fluid level switch.

2. Test for infinite resistance between the ground terminal A and the signal terminal B.

If less than the specified value, replace the brake fluid level switch.

2008 Chevrolet Silverado 1500

2008 BRAKES Hydraulic Brakes - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado