Suspension Control System - Automatic Level Control (Alcm) Cadillac DTS I

Fastener Tightening Specifications

Scheme 4

Scheme 5

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Automatic Level Control

Begin the system diagnosis with Diagnostic System Check - Vehicle . The Diagnostic System Check will provide the following information

1. The identification of the control module which command the system
2. The ability of the control module to communicate through the serial data circuit
3. The identification of any stored DTCs and their status

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Circuit/System Description

The automatic level control (ALC) module performs checks of internal calibration data. If a fault condition is detected, the ALC module will set the fault DTC, and may, depending upon the fault type, turn ON the SERVICE SUSPENSION SYSTEM message. Recovery from any controller fault condition is attempted only after the ignition is cycled ON and OFF.

Conditions for Running the DTC

1. Battery voltage is between 9-16 volts
2. Ignition is ON.

Conditions for Setting the DTC

1. The DTC is set when any calibration faults internal to the ALC module are detected.
2. The fault is detected during 3 consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with the scan tool.

Action Taken When the DTC Sets

1. The ALC module disables all ALC functionality.
2. The ALC module sends a message to the instrument panel cluster (IPC) to display the SERVICE SUSPENSION SYSTEM message.

Conditions for Clearing the DTC

A history DTC will clear when the ALC no longer senses the malfunction and the ignition is cycled ON and OFF.

Reference Information

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Verify that DTC C0558 is not set.

1. If the DTC is set, perform the «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) procedure. If the DTC resets replace the ALC sensor/module.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for automatic level control sensor/module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The automatic level control (ALC) position sensor provides a signal voltage between 0.5-4.85 volts to the ALC module. This signal voltage represents the wheel's position relative to the body. The ALC module provides a 5-volt reference and a low reference to the sensor.

1. Ignition voltage is between 9-16 volts.
2. Vehicle is in motion.

1. The ALC module detects the voltage at the position sensor signal circuit is less than 0.5 volt or greater than 4.75 volts for more than 500 milliseconds.
2. The ALC module detects that there is a wide variation of the signal voltage over a predetermined period of time.

ALC functionality is suspended.

The condition responsible for setting the DTC no longer exists.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Verify that DTC C0625 is not set.

1. If the DTC is set, perform the «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) procedure. If the DTC resets replace the ALC sensor/module.

Control Module References for automatic level control sensor/module replacement, setup, and programming

Repair Verification

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Use the scan tool Diagnostic Counter Reset output control function to bypass the 3 consecutive ignition cycle requirement for setting a DTC. This will ensure that if a DTC was to be reset during the repair verification process, it will be displayed on the scan tool.
5. Turn OFF the ignition for 60 seconds.
6. Turn ON the ignition.
7. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the and perform the appropriate diagnostic procedure.

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit Description

The automatic level control (ALC) module adjusts the vehicle suspension ride height. The ALC module determines the height of the vehicle based on the signal from the height sensor. The ALC module raises and lowers the vehicle in order to keep the vehicle level by controlling the exhaust valve and air compressor control circuits.

1. Battery voltage is between 9-16 volts.
2. The exhaust valve is commanded ON.

1. The exhaust solenoid control circuit is shorted to voltage, ground, or open when solenoid activation is commanded ON for 2.5 seconds.
2. The exhaust solenoid B+ circuit is shorted to ground or open when solenoid activation is commanded ON for 5 seconds.

The automatic level control (ALC) system will be inoperative.

Conditions for Clearing the MIL/DTC

1. DTC C0660 will change from a current DTC to a history DTC on the next ignition cycle.
2. DTC C0660 will be cleared from history after 50 ignition cycles.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the Exhaust Valve ON and OFF with a scan tool. The exhaust solenoid valve should turn ON and OFF with each command.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the automatic level control (ALC) compressor.
2. Verify that a test lamp illuminates between the B+ circuit terminal C and ground. If the test lamp does not illuminate, test the B+ circuits for a short to ground or an open/high resistance.
3. Connect a test lamp between the B+ circuit terminal C and the control circuit terminal A.
4. Command the exhaust valve ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ALC sensor/module. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ALC sensor/module.
5. If all circuits test normal, test or replace the ALC compressor.

1. «Air Compressor Replacement»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
2. «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
3. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for automatic level control sensor/module replacement, setup, and programming

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Use the scan tool Diagnostic Counter Reset output control function to bypass the 3 consecutive ignition cycle requirement for setting a DTC. This will ensure that if a DTC was to be reset during the repair verification process, it will be displayed on the scan tool.
5. Turn OFF the ignition for 60 seconds.
6. Turn ON the ignition.
7. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the and perform the appropriate diagnostic procedure.

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The electronic suspension control module (ESCM) adjusts the vehicle suspension ride height. The ESCM determines the height of the vehicle based on signals from the height sensors. The ESCM raises and lowers the vehicle in order to keep the vehicle level by controlling the exhaust valve and air compressor control circuits.

1. Battery voltage is between 9-16 volts.
2. The exhaust valve is commanded ON.

1. The exhaust solenoid control circuit is shorted to voltage, ground, or open when solenoid activation is commanded ON for 2.5 seconds.
2. The exhaust solenoid B+ circuit is shorted to ground or open when solenoid activation is commanded ON for 5 seconds.

1. The electronic suspension control system will be inoperative.
2. The SERVICE SUSPENSION SYSTEM message will be displayed.

1. DTC C0660 will change from a current DTC to a history DTC on the next ignition cycle.
2. DTC C0660 will be cleared from history after 50 ignition cycles.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the Exhaust Valve ON and OFF with the scan tool. The exhaust solenoid valve should turn ON and OFF with each command.

1. Ignition OFF, disconnect the automatic level control (ALC) compressor.
2. Verify that a test lamp illuminates between the B+ circuit terminal C and ground. If the test lamp does not illuminate, test the B+ circuits for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the ALC compressor.
3. Connect a test lamp between the B+ circuit terminal C and the control circuit terminal A.
4. Command the exhaust valve ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ESCM. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ESCM.
5. If all circuits test normal, test or replace the ALC compressor.

1. «Air Compressor Replacement»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
2. «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
3. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for electronic suspension control module replacement, setup, and programming

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Use the scan tool Diagnostic Counter Reset output control function to bypass the 3 consecutive ignition cycle requirement for setting a DTC. This will ensure that if a DTC was to be reset during the repair verification process, it will be displayed on the scan tool.
5. Turn OFF the ignition for 60 seconds.
6. Turn ON the ignition.
7. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the and perform the appropriate diagnostic procedure.

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The automatic level control (ALC) adjusts the vehicle suspension ride height. The automatic level control (ALC) module determines the height of the vehicle based on the signal from the rear height sensor which is supplied a 5-volt reference voltage from the module. The module raises and lowers the vehicle in order to keep the vehicle level.

Battery voltage is between 9-16 volts.

The module detects the position sensor 5-volt reference circuit is less than 4.75 volts or greater than 5.25 volts.

The ALC system will be inoperative.

1. When the fault is no longer present, DTC C0696 will change from a current DTC to a history DTC on the next ignition cycle.
2. DTC C0696 will be cleared from history after 50 ignition cycles.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Verify that DTC C0696 is not set.

1. If the DTC is set, perform the «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) procedure. If the DTC resets replace the ALC sensor/module.

Control Module References for automatic level control sensor/module replacement, setup and programming.

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Use the scan tool Diagnostic Counter Reset output control function to bypass the 3 consecutive ignition cycle requirement for setting a DTC. This will ensure that if a DTC was to be reset during the repair verification process, it will be displayed on the scan tool.
5. Turn OFF the ignition for 60 seconds.
6. Turn ON the ignition.
7. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the and perform the appropriate diagnostic procedure.

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The electronic suspension control module (ESCM) adjusts the vehicle suspension ride height. The ESCM determines the height of the vehicle based on the voltage from the suspension position sensors. The module grounds the ELC relay and the exhaust control solenoid to raise and lower the vehicle in order to keep the vehicle level.

1. The ESCM is powered up.
2. The ESCM is commanding the compressor ON.

1. The compressor relay coil control circuit is shorted to voltage, ground, or open for 5 seconds.
2. The compressor relay coil B+ circuit is shorted to ground, or open for 5 seconds.

1. The electronic suspension control system will be inoperative.
2. The SERVICE SUSPENSION SYSTEM message will be displayed.

The ESCM does not detect a failure during the self test.

Diagnostic Aids

This circuit is monitored during every functional operation of the compressor relay output and every 3.3 milliseconds when output is active. If a compressor relay fault is detected, the ESCM retries the output every 15 seconds to try to recover from the fault.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the compressor relay ON with a scan tool. Listen for the operation of the ELC CMPRSR relay and the automatic level control compressor.

1. Ignition OFF, disconnect the ELC relay from the rear fuse block.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground. If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the electronic suspension control module.
3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground or faulty ALC compressor motor. If all circuits test normal, test or replace the ELC relay.
4. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
5. Disconnect the harness connector at the air compressor.
6. Test for less than 1 ohm between the ALC compressor ground circuit terminal D and ground. If greater than 1 ohm, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the ALC compressor.
8. Connect a 40A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the ALC compressor is activated. If the ALC compressor does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the ALC compressor.
9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. Command the ALC compressor relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the electronic suspension control module. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the electronic suspension control module.
11. If all circuits test normal, test or replace the ELC relay.

Component Testing

Relay Test

1. Ignition OFF, disconnect the relay.
2. Test for 50-200 ohms between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified value, replace the relay.
4. Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms between terminals 30 and 87. If greater than the specified range, replace the relay.

1. «Relay Replacement (Attached to Wire Harness)»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) or «Relay Replacement (Within an Electrical Center)»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
2. «Air Compressor Replacement»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
3. «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
4. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for ESC module replacement, setup, and programming

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Use the scan tool Diagnostic Counter Reset output control function to bypass the 3 consecutive ignition cycle requirement for setting a DTC. This will ensure that if a DTC was to be reset during the repair verification process, it will be displayed on the scan tool.
5. Turn OFF the ignition for 60 seconds.
6. Turn ON the ignition.
7. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the and perform the appropriate diagnostic procedure.

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The automatic level control (ALC) module adjusts the vehicle suspension ride height. The ALC module determines the height of the vehicle based on the voltage from the suspension position sensor. The module grounds the ELC relay and the exhaust control solenoid to raise and lower the vehicle in order to keep the vehicle level.

1. The ALC module is powered up.
2. The ALC module is commanding the compressor ON.

1. The compressor relay coil control circuit is shorted to voltage, ground, or open for 5 seconds.
2. The compressor relay coil B+ circuit is shorted to ground, or open for 5 seconds.

The ALC system will be inoperative.

The ALC module does not detect a failure during the self test.

This circuit is monitored during every functional operation of the compressor relay output and every 3.3 milliseconds when output is active. If a compressor relay fault is detected, the ALC module retries the output every 15 seconds to try to recover from the fault.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the compressor relay ON with a scan tool. Listen for the operation of the ELC CMPRSR relay and the air suspension compressor.

1. Ignition OFF, disconnect the ELC relay from the rear fuse block.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground. If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the ALC sensor/module.
3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground or faulty ALC compressor motor. If all circuits test normal, test or replace the ELC relay.
4. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
5. Disconnect the harness connector at the air compressor.
6. Test for less than 1 ohm between the ALC compressor ground circuit terminal D and ground. If greater than 1 ohm, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the ALC compressor.
8. Connect a 40A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the ALC compressor is activated. If the ALC compressor does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the ALC compressor.
9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. Command the ALC compressor relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ALC sensor/module. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ALC sensor/module.
11. If all circuits test normal, test or replace the ELC relay.

Relay Test

1. Ignition OFF, disconnect the relay.
2. Test for 50-200 ohms between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified value, replace the relay.
4. Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms between terminals 30 and 87. If greater than the specified range, replace the relay.

1. «Relay Replacement (Attached to Wire Harness)»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) or «Relay Replacement (Within an Electrical Center)»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
2. «Air Compressor Replacement»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
3. «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
4. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for automatic level control sensor/module replacement, setup, and programming

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Use the scan tool Diagnostic Counter Reset output control function to bypass the 3 consecutive ignition cycle requirement for setting a DTC. This will ensure that if a DTC was to be reset during the repair verification process, it will be displayed on the scan tool.
5. Turn OFF the ignition for 60 seconds.
6. Turn ON the ignition.
7. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the and perform the appropriate diagnostic procedure.

Symptoms - Automatic Level Control

Review the system operation in order to familiarize yourself with the system functions. Refer to Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55) .

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the automatic level control suspension. Refer to «Checking Aftermarket Accessories»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__checking-aftermarket-accessories) .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Inspect for binding or damaged shock absorbers.

Intermittent

Electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Air Compressor Leak Test»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm__air-compressor-leak-test)
2. «Automatic Level Control System Leak Test»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
3. «Rear of Vehicle High (W/O F55)»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) or «Rear of Vehicle High (With F55)»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
4. «Rear of Vehicle Low (With F55)»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) or «Rear of Vehicle Low (W/O F55)»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)

Air Compressor Leak Test

Special Tools

1. J 22124-B Pressure Gage (0-300 psi). See «Special Tools»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) .
2. J 22124-91 Pressure Gage Adapter. See «Special Tools»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) .

Testing Procedure

1. Attach the J 22124-91 to the air dryer. See «Special Tools»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) .
2. Attach the J 22124-B to the J 22124-91 with the toggle valve on the opposite side of the air compressor. See «Special Tools»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) . Close the toggle valve.
3. Apply air pressure at the schrader valve. Pressurize until the J 22124-B reads 690 kPa (100 psi). See «Special Tools»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) .
4. Check the following areas using soap bubbles: Solenoid valve Air dryer to compressor head O-ring Air dryer cover Air compressor head gasket Air compressor head cover-If necessary, tighten the cover bolts to 5.6 N.m (50 lb in).

If a leak is found, replace the air compressor. Refer to Air Compressor Replacement .

Special Tools

J 22124-B Pressure Gage (0-300 psi). See Special Tools .

1. Disconnect the air tube from the air dryer.
2. Attach the air tube to the J 22124-B on the side opposite the toggle valve. See «Special Tools»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) .
3. Close the toggle valve.
4. Apply service air pressure to the service valve and pressurize until the J 22124-B reads 550 kPa (80 psi). See «Special Tools»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) .
5. Verify that the system maintains pressure for at least 1 minute. If the system does not maintain the specified pressure for the specified amount of time, check the shock absorber air sleeves, air tubes, and all connections for air leaks using a soapy water solution. Repair or replace any leaking components. Refer to «Air Tube Replacement»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) and «Shock Absorber Replacement (FE1, FE3)»(/cadillac/dts/i-2005-2011/remont/suspension-rear/#rear-suspension-system) «Shock Absorber Replacement (FE7)»(/cadillac/dts/i-2005-2011/remont/suspension-rear/#rear-suspension-system) .

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The automatic level control (ALC) system uses a combination level sensor/module, compressor, and exhaust valve to increase or decrease air pressure in the system to control trim height. Battery voltage is supplied to the exhaust valve and compressor relay. The ALC module controls the ground circuits that activate the exhaust valve and compressor relay which maintain trim height based on the level sensor input voltage.

Performing the Suspension Position Calibration procedure may correct the condition.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the exhaust valve ON and OFF with a scan tool. Listen for the exhaust valve clicking.

1. Ignition OFF, disconnect the harness connector at the ALC compressor.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal C and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Connect a test lamp between the control circuit terminal A and the B+ circuit terminal C.
4. Command the exhaust valve solenoid ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ALC sensor/module. If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ALC sensor/module.
5. If all circuits test normal, test or replace the ALC compressor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Air Compressor Replacement»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
2. «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
3. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for automatic level control sensor/module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The automatic level control (ALC) system uses the electronic suspension control module (ESCM), level sensors, compressor, and exhaust valve to increase or decrease air pressure in the system to control trim height. Battery voltage is supplied to the exhaust valve and compressor relay. The ESCM controls the ground circuits that activate the exhaust valve and compressor relay which maintain trim height based on the level sensor input voltage.

Performing the Suspension Position Calibration procedure may correct the condition.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the exhaust valve ON and OFF with a scan tool. Listen for the exhaust valve clicking.

1. Ignition OFF, disconnect the harness connector at the ALC compressor.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal C and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ELC fuse is open, test or replace the ALC compressor.
3. Connect a test lamp between the control circuit terminal A and the B+ circuit terminal C.
4. Command the exhaust valve solenoid ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ESCM. If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ESCM.
5. If all circuits test normal, test or replace the ALC compressor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Air Compressor Replacement»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
2. «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
3. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for ESCM replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The automatic level control (ALC) system uses the electronic suspension control module (ESCM), level sensors, compressor, and exhaust valve to increase or decrease air pressure in the system to control trim height. Battery voltage is supplied to the exhaust valve and compressor relay. The ESCM controls the ground circuits that activate the exhaust valve and compressor relay which maintain trim height based on the level sensor input voltage.

1. Inspect for leaking lines or components. Perform the «Automatic Level Control System Leak Test»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) and «Air Compressor Leak Test»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm__air-compressor-leak-test) as necessary.
2. Performing the «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) procedure may correct the condition.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the compressor relay ON and OFF with a scan tool. Listen for the compressor running or relay clicks.

1. Ignition OFF, disconnect the ELC relay from the rear fuse block.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground. If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground or faulty ALC compressor motor. If all circuits test normal, test or replace the ELC relay.
4. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
5. Disconnect the harness connector at the air compressor.
6. Test for less than 2 ohms between the ALC compressor ground circuit terminal D and ground. If greater than the specified value, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the ALC compressor.
8. Connect a 40A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the ALC compressor is activated. If the ALC compressor does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the ALC compressor.
9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. Command the ALC compressor relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ESCM. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ESCM.
11. Connect the ELC relay. Command the ALC compressor ON with a scan tool. Verify the compressor is running. If the compressor does not run, test or replace the relay.
12. Ignition OFF, disconnect the harness connector at the ALC compressor.
13. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal C and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ELC fuse is open, test or replace the ALC compressor.
14. Connect a test lamp between the control circuit terminal A and the B+ circuit terminal C.
15. Command the exhaust valve ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ESCM. If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ESCM.
16. If all circuits test normal, test or replace the ALC compressor.

Relay Test

1. Ignition OFF, disconnect the relay.
2. Test for 50-200 ohms between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified value, replace the relay.
4. Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms between terminals 30 and 87. If greater than the specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Relay Replacement (Attached to Wire Harness)»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) or «Relay Replacement (Within an Electrical Center)»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
2. «Air Compressor Replacement»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
3. «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
4. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for electronic suspension control module (ESCM) replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-system-check-vehicle) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/dts/i-2005-2011/remont/oem-general-information/#vehicle-diagnostic-information__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The automatic level control (ALC) system uses a combination level sensor/module, compressor, and exhaust valve to increase or decrease air pressure in the system to control trim height. Battery voltage is supplied to the exhaust valve and compressor relay. The ALC module controls the ground circuits that activate the exhaust valve and compressor relay which maintain trim height based on the level sensor input voltage.

1. Inspect for leaking lines or components. Perform the «Automatic Level Control System Leak Test»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) and «Air Compressor Leak Test»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm__air-compressor-leak-test) as necessary.
2. Performing the «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm) procedure may correct the condition.

Schematic Reference

Automatic Level Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic Level Control Description and Operation (With F55) or Automatic Level Control Description and Operation (W/O F55)

Electrical Information Reference

1. «Circuit Testing»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__circuit-testing)
2. «Connector Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__testing-for-intermittent-conditions-poor)
4. «Wiring Repairs»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-service-troubleshooting-diagnosis__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the compressor relay ON and OFF with a scan tool. Listen for the compressor running or relay clicks.

1. Ignition OFF, disconnect the ELC relay from the rear fuse block.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 87 and ground. If the test lamp illuminates, test the control circuit for a short to voltage.
3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal 87 for a short to ground or faulty ALC compressor motor. If all circuits test normal, test or replace the ELC relay.
4. Verify that a test lamp illuminates between the B+ circuit terminal 85 and ground. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
5. Disconnect the harness connector at the air compressor.
6. Test for less than 2 ohms between the ALC compressor ground circuit terminal D and ground. If greater than the specified value, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the ALC compressor.
8. Connect a 40A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the ALC compressor is activated. If the ALC compressor does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the ALC compressor.
9. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
10. Command the ALC compressor relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ALC sensor/module. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ALC sensor/module.
11. Connect the ELC relay. Command the ALC compressor ON with a scan tool. Verify the compressor is running. If the compressor does not run, test or replace the relay.
12. Ignition OFF, disconnect the harness connector at the ALC compressor.
13. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal C and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ELC fuse is open, test or replace the ALC compressor.
14. Connect a test lamp between the control circuit terminal A and the B+ circuit terminal C.
15. Command the exhaust valve ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ALC sensor/module. If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ALC sensor/module.
16. If all circuits test normal, test or replace the ALC compressor.

Relay Test

1. Ignition OFF, disconnect the relay.
2. Test for 50-200 ohms between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified value, replace the relay.
4. Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms between terminals 30 and 87. If greater than the specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Relay Replacement (Attached to Wire Harness)»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction) or «Relay Replacement (Within an Electrical Center)»(/cadillac/dts/i-2005-2011/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-introduction)
2. «Air Compressor Replacement»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
3. «Suspension Position Calibration»(/cadillac/dts/i-2005-2011/remont/electronic-suspension/#suspension-control-system-automatic-level-control-alcm)
4. «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for automatic level control sensor/module replacement, setup and programming

Automatic Level Control (ALC) Trimset Procedure

If the system is functioning abnormally, performing the ALC Trimset recalibration procedure may correct the condition. When a system component has been replaced, ALC Trimset calibration must be performed. In the scan tool Special Functions menu, select ALC Trimset and follow the screen prompts to perform the procedure. Once the process has been completed, the system should be fully functional.

Removal Procedure

1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/dts/i-2005-2011/remont/hoistjack/#general-information__lifting-jacking-the-vehicle) .
2. Remove the wheel from the vehicle. Refer to «Tire and Wheel Removal and Installation»(/cadillac/dts/i-2005-2011/remont/wheel-tire-system/#tires-and-wheels__tire-wheel-removal-installation) .
3. Disconnect the height sensor connector.
4. Disconnect the sensor link from the ball stud.
5. Loosen the sensor mounting nut.
6. Disengage the anti-rotation tab and slide the sensor downward.
7. Remove the sensor from the vehicle.

Installation Procedure

1. Insert head of the sensor mounting stud into the key hole.
2. Slide the sensor upward until the anti-rotation tab engages in the lower hole.
3. Tighten the sensor mounting nut. Tighten: Tighten the nut to 9 N.m (80 lb in).
4. Connect the sensor link on the ball stud.
5. Connect the height sensor connector.
6. Install the wheel on the vehicle. Refer to «Tire and Wheel Removal and Installation»(/cadillac/dts/i-2005-2011/remont/wheel-tire-system/#tires-and-wheels__tire-wheel-removal-installation) .
7. Lower the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/dts/i-2005-2011/remont/hoistjack/#general-information__lifting-jacking-the-vehicle) .
8. Refer to «Control Module References»(/cadillac/dts/i-2005-2011/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for replacement and setup information.

Scheme 6

At the rear shock absorbers, the air tube connectors are held on with spring clips which snap into the grooves of the shock absorber air fittings. Air tube connectors are sealed using two O-rings.

1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/dts/i-2005-2011/remont/hoistjack/#general-information__lifting-jacking-the-vehicle) .
2. Remove the air tube from the air dryer.
3. Remove the bolt and the harness tie from the air compressor bracket.
4. Remove both rear wheels. Refer to «Tire and Wheel Removal and Installation»(/cadillac/dts/i-2005-2011/remont/wheel-tire-system/#tires-and-wheels__tire-wheel-removal-installation) .
5. Disconnect the air tube from the left and right rear shock absorbers.
6. Remove the 2 metal clips from the air tube and the vehicle.
7. Remove the air tube with the 3 clips from the vehicle.

1. Connect the air tube to the air dryer.
2. Install the air tube with the harness tie and the bolt on the air compressor bracket.
3. Install the air tube on the vehicle with 3 clips.
4. Connect the air tube to the left and right rear shock absorbers.
5. Install 2 metal clips on the air tube and the vehicle. Place each clip immediately forward of the wheel house fold-over tabs on the LH and RH side of the vehicle.
6. Install both rear wheels. Refer to «Tire and Wheel Removal and Installation»(/cadillac/dts/i-2005-2011/remont/wheel-tire-system/#tires-and-wheels__tire-wheel-removal-installation) .
7. Lower the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/dts/i-2005-2011/remont/hoistjack/#general-information__lifting-jacking-the-vehicle) .

1. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/dts/i-2005-2011/remont/hoistjack/#general-information__lifting-jacking-the-vehicle) .
2. Disconnect the air tube from the air dryer.
3. Remove the bolt and the harness tie with the air tube from the air compressor bracket.
4. Remove the intake air filter from the vehicle.
5. Remove the vehicle harness connector from the air compressor connector.
6. Remove the 2 nuts, 2 bolts, and the air compressor assembly from the vehicle.
7. Slide the air compressor connector off of the connector anchor.
8. Remove 2 bolts and the heat shield from the air compressor bracket.

1. Install the heat shield on the air compressor bracket with 3 bolts. Do not install the fourth heat shield bolt. It must be installed after the air tube is connected. Tighten: Tighten the bolts to 4 N.m (35 lb in).
2. Install the air compressor connector to the connector anchor.
3. Install the air compressor assembly on the vehicle with 2 nuts and 2 bolts. Tighten: Tighten the bolts to 9 N.m (80 lb in). Tighten the 2 nuts to 9 N.m (80 lb in).
4. Connect the harness connector to the air compressor connector.
5. Install the intake air filter on the vehicle.
6. Connect the air tube to the air dryer.
7. Connect the air tube and the harness tie to the air compressor bracket with the bolt. Tighten: Tighten the bolt to 4 N.m (35 lb in).
8. Lower the vehicle.

Automatic Level Control Description & Operation (With F55)

The automatic level control (ALC) system maintains a desired rear suspension position under all types of towing, hauling, and loading conditions.

The system uses the electronic suspension control module (ESCM), ELC relay, ALC compressor assembly, air dryer, air lines, shock absorbers with integral air chambers, suspension position sensors, exhaust valve, driver information center (DIC), and the serial data circuit to perform the system functions.

When the vehicle is unloaded, the rear suspension is at a desired position, which is monitored by the ESCM using the position sensor signal voltage inputs. As weight is added to the rear of the vehicle, the position sensor's signal voltage inputs change. When the ESCM detects a steady substantial change in the position sensor signal voltages for at least 10 seconds, it responds by commanding ON the ELC relay, which activates the compressor causing the air pressure in the shock absorber chambers to inflate. This inflation raises the rear of the vehicle to regain the desired suspension position. When weight is removed from the vehicle, the ESCM responds by commanding ON the exhaust valve causing the air pressure in the shock absorber chambers to deflate. This deflation lowers the vehicle to regain the desired suspension position.

The compressor is a positive displacement piston air pump driven by a 12-volt DC permanent magnet motor. The compressor draws filtered air through an intake line attached to an under body rail. The compressed air is then run through a dryer containing a moisture-absorbing chemical that dries the compressed air before it is sent to the shock absorber chambers. Each time the compressor is activated, the ESCM commands ON the exhaust valve for 1.5 seconds to release air from the compression chamber in the compressor's cylinder head ensuring low motor current draw upon compressor activation. The ESCM also limits the amount of compressor run time to 255 seconds to protect the compressor components from thermal damage.

The system also performs a self test on each ignition ON cycle in which the ESCM commands the ELC relay ON, activating the compressor for 4 seconds then monitors the position sensor's signal voltage inputs to verify the compressor is functioning and the system is holding air pressure.

The ESCM has the ability to detect malfunctions within the ALC system. Any malfunctions detected will cause the DIC to display the SERVICE SUSPENSION SYSTEM message. For more information on other functions of the ESCM, refer to Electronic Suspension Control Description and Operation .

Automatic Level Control Description & Operation (W/O F55)

The automatic level control (ALC) system maintains a desired rear suspension position under all types of towing, hauling, and loading conditions.

The system uses the automatic level control module (ALCM) with an integral suspension position sensor, ELC relay, ALC compressor assembly, air dryer, air lines, LR and RR shock absorbers with integral air chambers, exhaust valve, driver information center (DIC), and the serial data circuit to perform the system functions.

When the vehicle is unloaded, the rear suspension is at a desired position, which is monitored by the ALCM using the integral position sensor signal voltage input. As weight is added to the rear of the vehicle, the position sensor signal voltage input changes. When the ALCM detects a steady substantial change in position sensor signal voltage for at least 10 seconds, it responds by commanding ON the ELC relay, which activates the compressor causing the air pressure in both rear shock absorber chambers to inflate. This inflation raises the rear of the vehicle to regain the desired suspension position. When weight is removed from the rear of the vehicle, the ALCM responds by commanding ON the exhaust valve causing the air pressure in both rear shock absorber chambers to deflate. This deflation lowers the rear of the vehicle to regain the desired suspension position.

The compressor is a positive displacement piston air pump driven by a 12-volt DC permanent magnet motor. The compressor draws filtered air through an intake line attached to an under body rail. The compressed air is then run through a dryer containing a moisture-absorbing chemical that dries the compressed air before it is sent to the shock absorber chambers. Each time the compressor is activated, the ALCM commands ON the exhaust valve for 1.5 seconds to release air from the compression chamber in the compressor's cylinder head ensuring low motor current draw upon compressor activation. The ALCM also limits the amount of compressor run time to 255 seconds to protect the compressor components from thermal damage.

The system also performs a self test on each ignition ON cycle in which the ALCM commands the ELC relay ON, activating the compressor for 4 seconds then monitors the position sensor signal voltage input to verify the compressor is functioning and the system is holding air pressure.

The ALCM has the ability to detect malfunctions within the ALC system. Any malfunctions detected will cause the DIC to display the SERVICE SUSPENSION SYSTEM message.

Illustration Tool Number/ Description J 22124-B Pressure Gage J 22124-91 Adapter Tube

Scheme 7

Scheme 8

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Component Connector End Views
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Control Module References
• Diagnostic Repair Verification
• Relay Replacement (Attached to Wire Harness)
• Checking Aftermarket Accessories
• Shock Absorber Replacement (FE1, FE3)
• Lifting and Jacking the Vehicle
• Tire and Wheel Removal and Installation
• Fastener Notice
• Electronic Suspension Control Description and Operation
• DTC C0558
• Automatic Level Control Description and Operation (With F55)
• Air Compressor Leak Test