GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2000 🢒 Seville 🢒 Suspension 🢒 Automatic Level Control 🢒 Rear of Vehicle Low

Rear of Vehicle Low w/o F45

Step

Action

Value(s)

Yes

No

1

Is any aftermarket equipment installed on the vehicle that could affect the ALC system?

--

Go to Step 2

Go to Step 4

2

Inspect the aftermarket equipment to ensure that it is not affecting ALC performance.

Is the aftermarket equipment affecting the ALC performance?

--

Go to Step 3

Go to Step 4

3

Correct the condition.

Is the condition corrected?

--

Go to Automatic Level Control System Operation Check

--

4

Inspect the IGN 3 fuse and ELC fuse for an open fuse.

Is the fuse open?

--

Go to Step 5

Go to Step 6

5

Important: If the fuse is open repeatedly, inspect CKT 41 (BRN) or CKT 1342 (RED) for a short to ground.

Replace the fuse.

Is the replacement or repair complete?

--

Go to Automatic Level Control System Operation Check

--

6

Inspect the height sensor and link for proper connection or damage.

Are the height sensor and the link properly connected and in good condition?

--

Go to Step 8

Go to Step 7

7

Reconnect or replace the height sensor or the link. Refer to Automatic Level Control Sensor and Bracket Replacement .

Is the repair or replacement complete?

--

Go to Automatic Level Control System Operation Check

--

8

Does the vehicle leak down when the vehicle is not used for an extended period of time (overnight), but then come up to normal trim height with vehicle use?

--

Go to Step 28

Go to Step 9

9
  1. Turn the ignition switch ON.
  2. Add approximately 136 kg (300 lbs) of weight to the rear of the vehicle.

Important: Allow 27 seconds for the air compressor to start and then additional time for the shock absorbers to inflate.

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

--

Go to Step 10

Go to Step 12

10

Is the trim height at the rear underbody points correct? Refer to Trim Height .

--

Go to Automatic Level Control System Operation Check

Go to Step 11

11

Adjust the height sensor. Refer to Automatic Level Control Sensor Adjustment .

Is trim height at the rear underbody points correct? Refer to Trim Height .

--

Go to Automatic Level Control System Operation Check

Repeat this Step

12

Did the air compressor operate when weight was added?

--

Go to Step 28

Go to Step 13

13
  1. Disconnect the height sensor electrical connector.
  2. Turn the ignition switch to the ON position.
  3. Connect a fused jumper from the height sensor connector (vehicle side), terminal B, to ground.

Did the air compressor operate?

--

Go to Height Sensor Operational Check

Go to Step 14

14
  1. Turn the ignition switch OFF.
  2. Connect the height sensor electrical connector.
  3. Remove the ELC relay from the rear junction block.
  4. Turn the ignition switch ON.
  5. Measure the voltage from the right rear terminal (where relay pin 85 was removed) to ground using a J 39200.

Is the measurement greater than the specified value?

10.5 V

Go to Step 16

Go to Step 15

15

Inspect for an open ELC fuse, or for an open circuit to the fuse or in the rear junction block. See Wiring Systems. Repair the open or replace the ELC fuse or the rear junction block as required.

Is the repair or replacement complete?

--

Go to Automatic Level Control System Operation Check

--

16

Measure the voltage from the right front terminal (where relay pin 30 was removed) to ground using a J 39200 (this terminal is hot at all times).

Is the measurement greater than the specified value?

10.5 V

Go to Step 18

Go to Step 17

17

Replace the rear junction block.

Is the replacement complete?

--

Go to Automatic Level Control System Operation Check

--

18
  1. Remove the ELC relay.
  2. Connect a J 39200 between the right rear terminal and left front terminal (where relay pins 85 and 86 were removed).

    3. Important: The ignition switch must be cycled if the ignition was left on from the previous step.

  3. Turn the ignition switch ON.

Did the measurement exceed the specified voltage after 17-27 seconds (17-27 seconds is the height sensor delay period)?

10.5 V

Go to Step 20

Go to Step 19

19

Inspect for a poor connection at the height sensor connector, terminal B, or an open in CKT 321.

Was a poor connection or an open found and corrected?

--

Go to Automatic Level Control System Operation Check

Go to Height Sensor Operational Check

20

Connect a 30-amp fused jumper from the right front terminal to the left rear terminal (where relay pins 30 and 87 were removed).

Did the air compressor operate?

--

Go to Step 21

Go to Step 22

21

Replace the ELC relay.

Is the replacement complete?

--

Go to Automatic Level Control System Operation Check

--

22
  1. Leave the jumper from the previous step in place.
  2. Disconnect the air compressor electrical connector.
  3. Measure the voltage from the air compressor electrical connector (vehicle side), terminal B, to ground using a J 39200.

Is the measurement greater than the specified value?

10.5 V

Go to Step 24

Go to Step 23

23
  1. Inspect the rear junction block connectors for a poor connection.
  2. If the connections are OK, repair the open in CKT 322.

Is the repair complete?

--

Go to Automatic Level Control System Operation Check

--

24
  1. Leave the jumper from the previous step in place.
  2. Measure the voltage from the air compressor connector (vehicle side), terminal B to terminal D, using a J 39200.

Is the measurement greater than the specified value?

10.5-15 V

Go to Step 26

Go to Step 25

25

Repair the open CKT 1050.

Is the repair complete?

--

Go to Automatic Level Control System Operation Check

--

26
  1. Disconnect the jumper and install the ALC relay.
  2. Connect a jumper from the air compressor connector (compressor side), terminal D, to ground.
  3. Connect a 30-amp fused jumper from the air compressor connector (compressor side), terminal B, to B+.

Did the air compressor operate?

--

Go to Step 13

Go to Step 27

27

Replace the air compressor. Refer to Air Compressor Replacement .

Is the replacement complete?

--

Go to Automatic Level Control System Operation Check

--

28

Inspect the following:

       Important: If the air sleeve is worn through, perform the residual air pressure check.

    • Rear shock absorbers for a leaking air sleeve.
    • Air tube for kinks or pinched tubes.
    • Air tube for a disconnected condition at the shock absorbers or at the air dryer.
    • All air tube connections using soap and water.

Was a leak or damage found and corrected?

--

Go to Automatic Level Control System Operation Check

Go to Step 29

29
  1. Disconnect the air tube from the air dryer.
  2. Connect the J 22124-91 pressure gage adapter to the air dryer.
  3. Connect the J 22124-B pressure gage to the J 22124-91 pressure gage adapter with the toggle valve on the opposite side (away from the air compressor) and closed.
  4. Disconnect the air compressor electrical connector.
  5. Connect a jumper from the air compressor electrical connector (compressor side), terminal D to ground.
  6. Connect a 30-amp fused jumper from the air compressor electrical connector (compressor side), terminal B, to B+.
  7. Allow the air compressor to operate until the pressure reaches 690 kPa (100 psi).
  8. Disconnect the jumper from terminal D when 690 kPa (100 psi) is reached.

Is the air compressor able to reach it 690 kPa (100 psi)?

690 kPa (100 psi)

Go to Step 31

Go to Step 30

30

Replace the air compressor. Refer to Air Compressor Replacement .

Is the replacement complete?

--

Go to Automatic Level Control System Operation Check

--

31

Does the air pressure reading on the J 22124-B pressure gage stay at 690 kPa (100 psi)?

690 kPa (100 psi)

Go to Step 32

Go to Air Compressor Leak Test

32
  1. Open the J 22124-B pressure gage toggle valve.
  2. Disconnect the vehicle air tube from the LH rear shock absorber.
  3. Connect the J 22124-B pressure gage adapter tube to the LH rear shock absorber and to the J 22124-B pressure gage.
  4. Reconnect the ground jumper to the air compressor connector terminal D (terminal B should still be connected to B+).

Is the air compressor able to reach 690 kPa (100 psi) and then maintain 690 kPa (100 psi) after the jumper is disconnected from terminal D?

690 kPa (100 psi)

Go to Step 34

Go to Step 33

33

Replace the LH rear shock absorber. Refer to Shock Absorber Replacement .

--

Go to Automatic Level Control System Operation Check

--

34
  1. Disconnect the adapter tube from the LH rear shock absorber.
  2. Connect the vehicle air tube to the LH rear shock absorber.
  3. Disconnect the vehicle air tube from the RH rear shock absorber.
  4. Connect the adapter tube to the RH rear shock absorber.
  5. Reconnect the ground jumper to the air compressor connector terminal D (terminal B should still be connected to B+).

Is the air compressor able to reach 690 kPa (100 psi)?

690 kPa (100 psi)

Go to Step 36

Go to Step 35

35

Replace the RH rear shock absorber. Refer to Shock Absorber Replacement .

Is the replacement complete?

--

Go to Automatic Level Control System Operation Check

--

36
  1. Disconnect the adapter tube from the RH rear shock absorber and the J 22124-B pressure gage. Do not connect the vehicle air tube.
  2. Disconnect the J 22124-91 pressure gage adapter from the air dryer and the J 22124-B pressure gage.
  3. Connect the vehicle air tube to the air dryer.
  4. Connect the J 22124-B pressure gage to the vehicle air tube at the RH rear shock absorber. The J 22124-B pressure gage toggle valve must be on the side of the gage away from the air tube.
  5. Close the J 22124-B pressure gage toggle valve.
  6. Reconnect the ground jumper to the air compressor connector terminal D (terminal B should still be connected to B+).

Is the air compressor able to reach 690 kPa (100 psi) and then maintain 690 kPa (100 psi) after the jumper is disconnected from terminal D?

690 kPa (100 psi)

Go to Step 38

Go to Step 37

37

Replace the air tube. Refer to Air Tube Replacement .

Is the replacement complete?

--

Go to Automatic Level Control System Operation Check

--

38

Inspect for a binding rear shock absorber.

Was a binding shock absorber found and replaced?

--

Go to Automatic Level Control System Operation Check

--

Rear of Vehicle Low w/ F45

Step

Action

Value(s)

Yes

No

1

Was the ALC System Check performed?

--

Go to Step 2

Go to Automatic Level Control System Operation Check

2
  1. Turn the ignition ON with the engine OFF.
  2. Listen for the ALC air compressor to activate.

Did the air compressor come on within 30 seconds?

30 seconds

Go to Step 9

Go to Step 3

3
  1. Turn the ignition OFF.
  2. Disconnect the ALC connector from the ALC air compressor assembly.
  3. Disconnect connector C1 from the CVRSS control module.
  4. Turn the ignition ON.
  5. Connect a jumper wire from CVRSS connector C1 (harness side), pin C15, to ground.
  6. Measure the voltage from the ALC air compressor connector (harness side), pin B, to ground.

Is the measurement greater than the specified value?

10 V

Go to Step 4

Go to Step 7

4
  1. Remove the jumper wire from pin C15.
  2. Turn the ignition OFF.
  3. Inspect for continuity from the ALC air compressor connector (harness side), pin D, to ground.

Is there continuity?

--

Go to Step 6

Go to Step 5

5
  1. Turn the ignition OFF.
  2. Repair the open in CKT 1050.

Is the repair complete?

--

Go to Automatic Level Control System Operation Check

--

6
  1. Replace the ALC air compressor. Refer to Air Compressor Replacement .
  2. Replace the air tube. Refer to Air Tube Replacement .

Is the repair complete?

--

Go to Step 12

--

7
  1. Remove the jumper wire from pin C15.
  2. Turn the ignition OFF.
  3. Inspect for the following:
    4. • open ELC fuse
    • open CKT 322
    • open CKT 321
    • open circuit in the Rear Junction Block

Was a problem found?

--

Go to Step 8

--

8

Repair the open or replace the fuse.

Is the repair complete?

--

Go to Automatic Level Control System Operation Check

--

9

Inspect the left and right rear position sensors for damage or disconnected links.

Are any damaged sensors or disconnected links present?

--

Go to Step 13

Go to Step 10

10

Perform the ALC System Leak Test.

Is a leak present?

--

Go to Step 11

Go to Step 12

11

Repair the leak in the ALC System.

Is the repair complete?

--

Go to Step 14

--

12
  1. Turn the ignition OFF.
  2. Connect the scan tool to the DLC.
  3. Turn the ignition switch ON with engine OFF.
  4. Perform the ALC Trim Height Adjustment. Refer to Trim Height Adjustment

Has the ALC trim height adjustment been completed?

--

Go to Step 14

--

13

Replace the damaged rear position sensor or reconnect the link. Refer to Electronic Suspension Rear Position Sensor Replacement .

Is the replacement complete?

--

Go to Automatic Level Control System Operation Check

--

14
  1. Reconnect all of the connectors that were removed.
  2. Clear the CVRSS DTCs. Refer to Clearing DTCs .
  3. Wait for at least 5 minutes.

Is the rear of the vehicle trim height correct? Refer to Trim Height .

--

System OK

Go to Step 12