GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Eldorado 🢒 Suspension 🢒 Road Sensing Suspension (RSS) 🢒 DTC C0662 or C0663

Circuit Description

The Electronic Level Control exhaust solenoid valve is switched ON or OFF by the Continuously Variable Road Sensing Suspension (CVRSS) module. The control module provides a low-side drive (switched to ground) whenever exhaust activity is required and during a head-relief sequence which occurs before each compressor start-up. This drive output from the CVRSS module is continually monitored to determine if the voltage level agrees with the commanded state.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

DTC C0662

The following conditions must be present to set the DTC:

    • The CVRSS module detects voltage less than a preset value in the exhaust solenoid control circuit during an exhaust solenoid valve OFF state test.
    • The fault is detected during three consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with a scan tool.

DTC C0663

The following conditions must be present to set the DTC:

    • The CVRSS module detects voltage greater than a preset value in the exhaust solenoid control circuit during an exhaust solenoid valve ON state test.
    • The fault is detected during three consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with a scan tool.

Action Taken When the DTC Sets
    • ALL rear leveling activity for the remainder of the ignition cycle will be disabled.
    • The SERVICE RIDE SYS message will be displayed.

Conditions for Clearing the MIL/DTC
    • The scan tool can be used to clear the DTC.
    • The DTC is saved as history when the CVRSS module no longer sees an out of range voltage condition in the exhaust solenoid control circuit. The DTC will clear if the fault does not return after 50 consecutive ignition cycles.

Diagnostic Aids

These DTCs are set only by electrical problems with the ELC exhaust solenoid control circuit. Pneumatic blockage problems do not set these DTCs.

A temporary compressor overload, such as high head pressure during a cold start, may cause the ELC fuse to open. This is one possible cause of DTC C0662.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Tests for voltage in the ALC exhaust solenoid control circuit.

    2.

  2. Tests for a short to voltage in the ALC exhaust solenoid control circuit.

    3.

  3. Tests for voltage in the battery positive voltage circuit of the ALC compressor in order to isolate a short to ground or an open.

Step

Action

Yes

No

Schematic Reference: Automatic Level Control Schematics

1

Did you perform the Road Sensing Suspension Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Road Sensing Suspension

2

  1. Disconnect the CVRSS module connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Connect a test lamp between the ALC exhaust solenoid control circuit of the CVRSS module and a good ground.

Does the test lamp illuminate?

Go to Step 3

Go to Step 4

3

  1. Turn OFF the ignition.
  2. Disconnect the ALC compressor connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the ALC exhaust solenoid control circuit of the CVRSS module and a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 7

4

  1. Turn OFF the ignition.
  2. Disconnect the ALC compressor connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the battery positive voltage circuit of the ALC compressor and a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 8

5

Test the ALC exhaust solenoid control circuit for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 6

6

Inspect for poor connections at the ALC compressor connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

7

Inspect for poor connections at the CVRSS module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

8

Repair the short to ground or the open in the battery positive voltage circuit of the ALC compressor connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 12

--

9

Repair the short to voltage in the ALC exhaust solenoid control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 12

--

10

Replace the ALC compressor head. Refer to Automatic Level Control Air Compressor Head Replacement in Automatic Level Control.

Did you complete the replacement?

Go to Step 12

--

11

Important: Perform the set up procedure for the CVRSS module .

Replace the CVRSS module. Refer to Electronic Suspension Control Module Replacement .

Did you complete the replacement?

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK