Schematic Reference: Automatic Level Control Schematics

Did you review the Automatic Level Control System Description and Operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Automatic Level Control

1. Turn ON the ignition, with the engine OFF.
2. Add a load of 135 kg (300 lbs) to the rear of the vehicle.

Does the automatic level control (ALC) compressor operate?

Go to Step 3

Go to Step 4

Does the rear of the vehicle rise and not leak down?

Go to Automatic Level Control Sensor Adjustment

Go to Automatic Level Control System Leak Test

1. Disconnect the automatic level control sensor connector.
2. Connect a test lamp between the battery positive voltage circuit of the automatic level control (ALC) sensor and a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 14

Connect a test lamp between the battery positive voltage circuit and the ground circuit of the ALC sensor.

Does the test lamp illuminate?

Go to Step 6

Go to Step 15

Connect a test lamp between the automatic level control relay coil supply voltage circuit and a good ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 11

Connect a 10 amp fused jumper wire between the automatic level control relay coil supply voltage circuit and a good ground.

Does the ALC activate?

Go to Step 16

Go to Step 8

1. Leave the 10 amp fused jumper wire connected between the automatic level control relay coil supply voltage circuit and a good ground
2. Disconnect the ALC compressor connector.
3. Connect a test lamp between the automatic level control compressor motor control circuit and a good ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 9

Test the automatic level control compressor motor control circuit for a short to ground or an open.

Did you find and correct the condition?

Go to Step 19

Go to Step 13

Test the ALC compressor harness for a poor connection or an open. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs or Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 18

Test the automatic level control relay coil supply voltage circuit for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 12

Test the ignition 1 voltage circuit to the ELC relay for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 17

Test the battery positive voltage circuit to the ELC relay for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 17

Repair the open in the battery positive voltage circuit to the ALC sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

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Repair the open in the ALC sensor ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

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Replace the ALC sensor. Refer to Automatic Level Control Sensor and Bracket Replacement .

Did you complete the replacement?

Go to Step 19

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Replace the ELC relay.

Did you complete the replacement?

Go to Step 19

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Replace the ALC compressor. Refer to Air Compressor Replacement .

Did you complete the replacement?

Go to Step 19

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Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3