Schematic Reference: Air Brake System Schematics

Connector End View Reference: Air Brake System Connector End Views

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 - Air Brakes

Verify the condition is present.

Does the system operate normally?

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Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

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

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

480 kPa (70 psi)

Go to Step 4

Go to Air Brake System Testing

1. Turn OFF the ignition.
2. Disconnect one of the low air pressure switches.
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 other 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 6

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

Did you find and correct the condition?

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Go to Step 9

Go to Step 8

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 9

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Replace the instrument panel cluster. Refer to Instrument Cluster Replacement .

Is the replacement complete?

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Go to Step 9

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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