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Chevrolet Silverado / GMC Sierra. 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
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