Schematic Reference: Brake Warning System Schematics

1

Did you review the Brake Warning System Description and Operation and perform the necessary inspections?

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Go to Step 2

Go to Symptoms - Hydraulic Brakes

Verify a fault is present.

Does the system operate normally?

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Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

1. Start the vehicle.
2. Inspect the air pressure gage.

Does the air pressure gauge indicate the air pressure is above the specified value?

480 kPa (70 psi)

Go to Step 4

Go to Air Brake System Leak Test

1. Turn OFF the ignition.
2. Disconnect the Low Air Pressure Switch.
3. Turn ON the ignition.

Does the low air indicator turn OFF?

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Go to Step 7

Go to Step 5

1. Turn OFF the ignition.
2. Disconnect the Multifunction Alarm Module.
3. Turn ON the Ignition.

Does the low air indicator turn OFF?

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Go to Step 6

Go to Step 8

Replace the Multifunction Alarm Module. Refer to Multifunction Alarm Module Replacement in Instrument Panel, Gages, and Console.

Did you complete the replacement?

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Go to Step 10

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Replace the Low Air Pressure Switch. Refer to Low Air Pressure Switch Replacement .

Did you complete the replacement?

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Go to Step 10

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Inspect the low air indicator control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 10

Go to Step 9

Replace the Instrument Panel Cluster.

Is the replacement complete?

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Go to Step 10

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Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2