For 1990-2009 cars

### Tools Required

J 22124-B Pressure Gage (0-300 psi)

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
DEFINITION: The rear of the vehicle will not raise, is always low, or leaks down when the vehicle is not used.
1 | Is any aftermarket equipment installed on the vehicle that could affect the ALC system? | -- | Go to Step 2 | Go to Step 4
2 | Check 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 | Check the ELC fuse in the RH MaxiFuse® Block and the ABS/CCR fuse in the IP Fuse Block for an open (blown) condition. Is the fuse open? | -- | Go to Step 5 | Go to Step 6
5 | Replace the fuse. NOTE: If the fuse is open (blown) repeatedly, check CKT 641 (BRN) or CKT 1042 (RED) for a short circuit to ground condition. Is the replacement complete? | -- | Go to Automatic Level Control System Operation Check | --
6 | Check the height sensor and link for proper connection and 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 to the ON position.
2. Add approximately 300 lbs of weight to the rear of the vehicle.

Does the rear of the vehicle rise and not leak down? NOTE: Allow 27 seconds for the air compressor to start and then additional time for the struts to inflate.

--

Go to Step 10

Go to Step 12

10 | Is the trim height at the rear underbody points correct? Refer to Trim Height in Suspension General Diagnosis. | 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 in Suspension General Diagnosis. | 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.

Is the air compressor operating?

--

Go to Height Sensor Operational Check

Go to Step 14

14 |

1. Turn the ignition switch to the OFF position.
2. Connect the height sensor electrical connector.
3. Remove the ELC relay from the IP junction block.
4. Turn the ignition switch to the ON position.
5. Measure the voltage from the terminal where relay pin 85 was removed to ground.

Is battery voltage present?

Battery Voltage

Go to Step 16

Go to Step 15

15 | Repair the open circuit condition in circuit 641 (BRN). Is the replacement or repair complete? | -- | Go to Automatic Level Control System Operation Check | --
16 | Measure the voltage from the terminal where relay pin 30 was removed to ground (this terminal is hot at all times). Is battery voltage present? | Battery Voltage | Go to Step 18 | Go to Step 17
17 | Repair the open circuit condition in circuit 1042 (RED) between the RH MaxiFuse® block and the IP junction block. Is the repair complete? | -- | Go to Automatic Level Control System Operation Check | --
18 |

1. Connect a voltmeter between the terminals where relay pins 85 and 86 were removed.
2. Turn the ignition switch to the ON position. NOTE: The ignition switch must be cycled if the ignition was left on from the previous step.

Is battery voltage present after 17 to 27 seconds (17 to 27 seconds is the height sensor delay period).

Battery Voltage

Go to Step 20

Go to Step 19

19 | Check for a poor connection at the height sensor connector, terminal B, or an open-circuit condition in circuit 321. Was a poor connection or open-circuit condition found and corrected? | -- | Go to Automatic Level Control System Operation Check | Go to Height Sensor Operational Check
20 | Connect a 30-amp fused jumper between the terminals where relay pins 30 and 87 were removed. Is the air compressor operating? | -- | 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 C, to ground.

Is battery voltage present?

Battery Voltage

Go to Step 24

Go to Step 23

23 | Repair the open-circuit condition in circuit 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 C, to the same connector, terminal A.

Is battery voltage present?

Battery Voltage

Go to Step 26

Go to Step 25

25 | Repair the open-circuit condition in CKT 1250 (BLK). Is the repair complete? | -- | Go to Automatic Level Control System Operation Check | --
26 |

1. Disconnect the jumper and install the ALC relay.
2. Jumper the air compressor connector (compressor side), terminal A, to ground.
3. Jumper the air compressor connector (compressor side), terminal C to B+ using a 30-amp fused jumper wire.

Is the air compressor operating?

--

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 | Check the following:

• | Rear struts for a leaking air sleeve. NOTE: If the air sleeve is worn through, perform the Residual Air Pressure Check .

• | Air tube for kinks or pinched tubes.

• | Air tubes for a disconnected condition

• | 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-B adapter tube to the air dryer.
3. Connect the J 22124-B gage to the J 22124-B adapter tube with the toggle valve on the opposite side (away from the air compressor) and closed.
4. Disconnect the air compressor electrical connector.
5. Jumper the air compressor electrical connector (compressor side), terminal A to ground.
6. Jumper the air compressor electrical connector (compressor side), terminal C, to B+ using a 30-amp fused jumper wire.
7. Allow the air compressor to operate until the pressure reaches 690 kPa (100 psi).
8. Disconnect the jumper from terminal A 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 stay at 690 kPa (100 psi)? | 690 kPa (100 psi) | Go to Step 32 | Go to Air Compressor Leak Test
32 | One of the following components is leaking:

• | Air Tube (air dryer to pressure limiter valve)

• | Pressure Limiter Valve

• | Air Tube (pressure limiter valve to crossover air tube or air inflator valve (vehicles equipped with optional inflator valve only)

• | Inflator Valve (vehicles equipped with optional inflator valve only)

• | Crossover Air Tube (routed between the struts)

Replace the component with the leak.

Is the replacement complete?

Go to Automatic Level Control System Operation Check