1. Backprobe the low air pressure switch with a J 39200 DMM from terminal B to B+.
2. Measure the voltage.

Is the voltage less than the specified value?

10.0 V

Go to Step 2

Go to Step 3

Repair the open in CKT 150 (BLK) between the low air pressure switch and G 107.

Is the primary brake indicator lamp or the continuous tone inoperative?

--

Go to Step 3

System OK

1. Disconnect the low air pressure switch.
2. Connect a fused jumper from low air pressure switch connector terminal A to B.
3. Turn the ignition switch to RUN.
4. Observe the lamp.

Did the test lamp light?

--

Go to Step 4

Go to Step 5

Replace the low air pressure switch. Refer to Low Air Pressure Switch Replacement .

Is the primary brake indicator lamp or the continuous tone inoperative?

--

Go to Step 5

System OK

1. Leave the jumper connected.
2. Backprobe the multifunction alarm module with a J 39200 DMM from terminal B5 to B+.
3. Measure the voltage.

Is the voltage less than the specified value?

10.0 V

Go to Step 6

Go to Step 7

Repair the open in CKT 33, CKT 602, CKT 606 (TAN/WHT), or CKT 9 (BRN) between the low air pressure switch, the instrument cluster, and the multifunction alarm module.

Is the primary brake indicator lamp or the continuous tone inoperative?

--

--

System OK

Replace the multifunction alarm module. Refer to Multifunction Alarm Module Replacement .

Is the primary brake indicator lamp or the continuous tone inoperative?

--

--

System OK