GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the ALC Suspension System Check?

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Go to Step 2

Go to Automatic Level Control Suspension System Check

2

  1. Ensure that the load leveling inflator switch is in the OFF position.
  2. Turn the ignition switch to the LOCK position.
  3. Disconnect the load leveling pump connector.
  4. Turn the ignition switch to the RUN position. Do not start the engine.
  5. Test CKT 1840 (ORN) at terminal E for an open circuit.

Is an open present in CKT 1840 (ORN)?

--

Go to Step 3

Go to Step 4

3

Repair the open in CKT 1840 (ORN).

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

4

Test CKT 639 (PNK) at terminal A for an open circuit.

Is an open present in CKT 639 (PNK)?

--

Go to Step 5

Go to Step 6

5

Repair the open in CKT 639 (PNK).

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

6

Test CKT 1350 (BLK) at terminal G for an open circuit.

Is an open present in CKT 1350 (BLK)?

--

Go to Step 7

Go to Step 8

7

Repair the open in CKT 1350 (BLK).

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

8

  1. Turn the ignition switch to the LOCK position.
  2. Reconnect the load leveling pump.
  3. Disconnect the load leveling height sensor.
  4. Turn the ignition switch to the RUN position. Do not start the engine.
  5. Test CKT 639 (PNK) at terminal D for an open circuit.

Is an open present in CKT 639 (PNK)?

--

Go to Step 9

Go to Step 10

9

Repair the open in the CKT 639 (PNK) between the load leveling height sensor and S473.

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

10

Test CKT 1350 (BLK) at terminal A for an open circuit.

Is an open present in CKT 1350 (BLK)?

--

Go to Step 11

Go to Step 12

11

Repair the open in CKT 1350 (BLK).

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

12

Test CKT 1298 (LT BLU) at terminal C for an open circuit.

Is an open present in CKT 1298 (LT BLU)?

--

Go to Step 22

Go to Step 13

13

Connect a fused jumper wire from terminal B, CKT 321 (YEL) to ground.

Does the pump start and run?

--

Go to Step 14

Go to Step 15

14

Replace the load leveling height sensor. Refer to Automatic Level Control Sensor and Bracket Replacement .

Is the replacement complete?

--

Go to Automatic Level Control Suspension System Check

--

15

Connect a fused jumper wire from the load leveling pump connector terminal D at CKT 321 (YEL) to ground.

Does the pump start and run?

--

Go to Step 16

Go to Step 17

16

Repair the open in CKT 321 (YEL) between the load leveling pump and the load leveling height sensor.

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

17

  1. Turn the ignition switch to the OFF position.
  2. Remove the load leveling pump .
  3. Inspect following circuits for opens:
  4. • CKT 639 (ORN) to the relay
    • CKT 321 (YEL) to the relay
    • CKT 1840 (ORN) to the relay
    • CKT 1350 (BLK) to the motor bracket

Did you find an open circuit?

--

Go to Step 18

Go to Step 19

18

Repair the open circuit.

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

19

  1. Reconnect the load leveling pump connectors.
  2. Connect a test lamp at the load leveling pump relay for the BLK/LT GRN wire.
  3. Turn the ignition switch to the RUN position. Do not start the engine.
  4. Wait 40 seconds.

Does the test lamp illuminate?

--

Go to Step 21

Go to Step 20

20

Replace the load leveling pump relay. Refer to Air Compressor Relay Replacement .

Is the replacement complete?

--

Go to Automatic Level Control Suspension System Check

--

21

Replace the load leveling pump. Refer to Air Compressor Replacement .

Is the replacement complete?

--

Go to Automatic Level Control Suspension System Check

--

22

  1. Access the load leveling timer relay.
  2. Test CKT 1298 (LT BLU) at terminal B of the load leveling timer relay for an open circuit.

Is an open present in CKT 1298 (LT BLU)?

--

Go to Step 23

Go to Step 24

23

Repair the open in CKT 1298 (LT BLU) between the load leveling timer relay and the load leveling height sensor.

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

24

Test CKT 1840 (ORN) at terminal D for an open circuit.

Is an open present in CKT 1840 (ORN)?

--

Go to Step 25

Go to Step 26

25

Repair the open in CKT 1840 (ORN).

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

26

Replace the load leveling timer relay. Refer to Automatic Level Control Relay Replacement .

Is the replacement complete?

--

Go to Automatic Level Control Suspension System Check

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