For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
DEFINITION: The rear of the vehicle is above trim height.
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 link properly connected and in good condition? | -- | Go to Step 8 | Go to Step 7
7 | Reconnect or replace the height sensor or 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 |

1. Turn the ignition switch to the ON position.

Important: The vehicle must be raised on a drive-on lift or be supported at the rear under the rear axle. Full vehicle weight must be on the rear suspension.

2. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
3. Disconnect the link from the height sensor. Refer to Automatic Level Control Sensor and Bracket Replacement .
4. Move the height sensor lever down so that it is approximately 45 degrees below level (to the floor) and hold it there.

Will the rear of the vehicle lower to trim level or below? NOTE: The height sensor has a 17 to 27 second delay period before the exhaust solenoid is activated.

--

Go to Step 9

Go to Step 10

9 | 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
10 | Move the height sensor lever up so that it is approximately 45 degrees above level (to the floor) and hold it there for a minimum of 27 seconds (17 to 27 seconds is the height sensor delay period). Does the air compressor come on? | -- | Go to Step 11 | Go to Height Sensor Operational Check
11 | Disconnect the air tube from the air dryer. Will the rear of the vehicle lower to trim level or below? | -- | Go to Step 19 | Go to Step 12
12 |

1. Connect the link to the height sensor lever.
2. Disconnect the air tube from both struts.

Will the rear of the vehicle lower to trim level or below?

--

Go to Step 13

Go to Step 14

13 | One of the following components is restricted:

• | 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 obstruction.

Is the replacement complete?

--

Go to Automatic Level Control System Operation Check

--

14 | Is the vehicle uneven (more than 19 mm (0.75 in) from side to side at the rear? | -- | Go to Step 16 | Go to Step 15
15 | Replace both rear springs. Refer to Coil Spring Replacement in Rear Suspension. Is the trim height at the rear underbody points correct? Refer to Trim Height in Suspension General Diagnostics. | Trim Height | Go to Automatic Level Control System Operation Check | --
16 |

1. Note which side of the vehicle is high.
2. Bounce the rear of the vehicle three times.

Is the vehicle still uneven more than 19 mm (0.75 in) from side to side at the rear?

--

Go to Step 17

Go to Step 18

17 | Replace the rear spring on the side of the vehicle that is high. Refer to Coil Spring Replacement in Rear Suspension. Is the trim height at the rear underbody points correct? Refer to Trim Height in Suspension General Diagnostics. | Trim Height | Go to Automatic Level Control System Operation Check | Repeat this Diagnostic Table
18 | Replace the rear strut on the side of the vehicle that is high. Refer to Strut Assembly Replacement in Rear Suspension. Is the trim height at the rear underbody points correct? Refer to Trim Height in Suspension General Diagnostics. | Trim Height | Go to Automatic Level Control System Operation Check | Repeat this Diagnostic Table
19 |

1. Raise the rear of the vehicle up as much as possible by holding the height sensor up. NOTE: The height sensor has a 17 to 27 second delay period before the air compressor is activated.
2. Reconnect the link to the height sensor.
3. Disconnect the air compressor electrical connector.
4. Check for continuity between terminals D and B of the air compressor connector.

Is continuity present?

Continuity

Go to Step 21

Go to Step 20

20 | Replace the air compressor head. Refer to Automatic Level Control Air Compressor Head Replacement . Is the replacement complete? | -- | Go to Automatic Level Control System Operation Check | --
21 | Measure the voltage between the air compressor electrical connector (vehicle side), terminal D and ground. Is battery voltage present? | Battery Voltage | Go to Step 23 | Go to Step 22
22 | Repair the open circuit condition in CKT 1042 (RED). Is the repair complete? | -- | Go to Automatic Level Control System Operation Check | --
23 |

1. Cycle the ignition switch and return it to the ON position.
2. Measure the voltage from the air compressor electrical connector (vehicle side), terminal D to the same connector, terminal B. NOTE: The link must be connected. Voltage will not be present within 17 to 27 seconds of the ignition switch cycle (height sensor delay). Voltage will not be present after approximately seven minutes.

Is battery voltage present?

Battery Voltage

Go to Step 25

Go to Step 24

24 | Check for an open circuit condition in circuit 320. Also, check for a poor connection at the height sensor connector. Was an open circuit or poor connection found and repaired? | -- | Go to Automatic Level Control System Operation Check | Go to Height Sensor Operational Check
25 | Replace the air compressor head. Refer to Automatic Level Control Air Compressor Head Replacement . Is the replacement complete? | -- | Go to Automatic Level Control System Operation Check | --