W/O F55

DTC C0660 (W/O F55)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.


DTC Descriptors
DTC C0660 01
- Level Control Exhaust Circuit Short to Battery

DTC C0660 06
- Level Control Exhaust Circuit Short to Ground or Open Circuit



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.

Conditions for Running the DTC

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


Conditions for Setting the DTC

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


Action Taken When the DTC Sets

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

Conditions for Clearing the MIL/DTC

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


Reference Information
Schematic Reference

Automatic Level Control Schematics (Automatic Level Control)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Automatic Level Control Description and Operation (W/O F55) (Automatic Level Control Description and Operation (w/o F55))Automatic Level Control Description and Operation (With F55) (Automatic Level Control Description and Operation (With F55))
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

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

Important: Whenever repairing and/or replacing ALC system components, perform the Suspension Position Calibration procedure.


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. With a scan tool, clear all ALC DTCs.
5. 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.

6. If all circuits test normal, test or replace the ALC compressor.


Repair Instructions

* Air Compressor Replacement (Service and Repair)
* Suspension Position Calibration (Programming and Relearning)
* Control Module References (Programming and Relearning) for ALC 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.