GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the ALC Suspension System Check?

--

Go to Step 2

Go to Automatic Level Control Suspension System Check

2

  1. Turn the ignition switch to the LOCK position.
  2. Disconnect the load leveling air inflator switch.
  3. Disconnect the load leveling air direction valve.
  4. Test CKT 1350 (BLK) at terminal B of the load leveling air inflator switch for an open circuit.

Is an open present in CKT 1350 (BLK)?

--

Go to Step 3

Go to Step 4

3

Repair the open in CKT 1350 (BLK) between the component and ground.

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

4

Test CKT 1350 (BLK) at terminal B of the load leveling air direction valve for an open circuit.

Is an open present in CKT 1350 (BLK)?

--

Go to Step 3

Go to Step 5

5

  1. Turn the ignition switch to the RUN position. Do not start the engine.
  2. Connect a fused jumper wire from terminal A of the load leveling air inflator switch to ground.

Does the load leveling pump run?

--

Go to Step 6

Go to Step 7

6

Replace the load leveling air inflator switch. Refer to Automatic Level Control Inflator Air Switch Replacement .

Is the replacement complete?

--

Go to Automatic Level Control Suspension System Check

--

7

  1. Turn the ignition switch to the RUN position. Do not start the engine.
  2. Connect a fused jumper wire from terminal E, CKT 321 (YEL) at the load leveling timer relay to ground.

Does the load leveling pump run?

--

Go to Step 9

Go to Step 8

8

Repair the open in CKT 321 (YEL) between the load leveling timer relay and S472.

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

9

  1. Ensure that the jumper wire remains connected.
  2. Test CKT 1249 (DK BLU) at terminal A of the load leveling air direction valve for voltage.

Is battery voltage present?

--

Go to Step 13

Go to Step 10

10

  1. Ensure that the jumper wire remains connected.
  2. Test CKT 1249 (DK BLU) terminal C of the load leveling timer relay for voltage.

Is battery voltage present?

--

Go to Step 11

Go to Step 12

11

Repair the open in CKT 1249 (DK BLU).

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

--

12

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

--

13

Measure the resistance of the load leveling air direction valve.

Is the resistance within the specified range?

20-100 ohms

Go to Step 15

Go to Step 14

14

Replace the load leveling air direction valve. Refer to Automatic Level Control Solenoid Valve Replacement .

Is the replacement complete?

--

Go to Automatic Level Control Suspension System Check

--

15

  1. Turn the ignition switch to the LOCK position.
  2. Disconnect the load leveling timer relay.
  3. Test CKT 1267 (PPL) for a short to ground.

Is a short to ground present in CKT 1267 (PPL)?

--

Go to Step 16

Go to Step 12

16

Repair the short to ground in CKT 1267 (PPL).

Is the repair complete?

--

Go to Automatic Level Control Suspension System Check

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