For 1990-2009 cars

### Circuit Description

The low air indicator illuminates when ground is applied to the low air indicator control circuit.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Brake Warning System Schematics
1 | Did you review the Brake Warning System Description and Operation and perform the necessary inspections? | -- | Go to Step 2 | Go to Brake Warning System Description and Operation
2 | Verify a fault is present. Does the system operate normally? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3
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 Testing

4 |

1. Turn OFF the ignition.
2. Disconnect the low air pressure switch.
3. Turn ON the ignition.

Does the low air indicator turn OFF?

--

Go to Step 7

Go to Step 5

5 |

1. Turn OFF the ignition.
2. Disconnect the multifunction alarm module.
3. Turn ON the ignition.

Does the low air indicator turn OFF?

--

Go to Step 6

Go to Step 8

6 | Replace the multifunction alarm module. Refer to Multifunction Alarm Module Replacement in Instrument Panel, Gages, and Console. Did you complete the replacement? | -- | Go to Step 10 | --
7 | Replace the low air pressure switch. Refer to Low Air Pressure Switch Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
8 | 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? | -- | Go to Step 10 | Go to Step 9
9 | Replace the instrument panel cluster. Is the replacement complete? | -- | Go to Step 10 | --
10 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2