GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Tahoe - 2WD 🢒 DTC 🢒 DTC C0660

Circuit Description

The exhaust solenoid valve is switched on and off via the suspension control module. The suspension control module provides a switched path to ground whenever exhaust activity is required and during a compressor "head-relief" sequence which occurs at compressor start-up if system pressure is lower than 68.95 kPa (10 psi). The suspension control module continually monitors the exhaust solenoid valve circuitry to determine if the voltage level agrees with the commanded state.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0660 Level Control Exhaust Valve Circuit

Conditions for Running the DTC

Whenever the exhaust solenoid valve is activated.

Conditions for Setting the DTC
    • An open in the control circuit of the exhaust solenoid valve
    • A short to ground in the control circuit of the exhaust solenoid valve
    • A short to battery in the control circuit of the exhaust solenoid valve
    • An open in the battery positive voltage circuit of the exhaust solenoid valve
    • An open RTD fuse
    • A malfunctioning exhaust solenoid valve

Action Taken When the DTC Sets
    • The exhaust solenoid valve is disabled for the remainder of the ignition cycle.
    • Stores a DTC C0660 in the suspension control module memory.

Conditions for Clearing the DTC
    • The suspension control module no longer detects a open, short to ground, or a short to battery in the control circuit of the exhaust solenoid valve.
    • Using a scan tool
    • A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids

The following conditions may cause a malfunction to occur in the exhaust solenoid valve:

    • A short to ground in the control circuit
    • An open in the control circuit
    • A short to battery in the control circuit
    • An open in the battery positive voltage circuit

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Command both the ON and OFF states. Repeat the commands as necessary.

  2. Test the exhaust solenoid valve resistance.

    3.

  3. Tests for voltage at the coil side of the exhaust solenoid valve. The RTD fuse supplies power to the coil side of the exhaust solenoid valve.

    4.

  4. Verifies that the suspension control module is providing ground to the exhaust solenoid valve.

    5.

  5. Tests if ground is constantly being applied to the exhaust solenoid valve.

    6.

  6. Test the control circuit of the exhaust solenoid valve for a short to voltage and an open.

  7. The replacement suspension control module must be calibrated.

Step

Action

Values

Yes

No

Schematic Reference: Automatic Level Control Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the exhaust ON and OFF.

Does the exhaust solenoid valve turn ON and OFF with each command?

--

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the automatic level control (ALC) compressor harness connector.
  3. Measure the resistance of the exhaust valve.

Does the resistance measure within the specified value?

18-45 Ω

Go to Step 4

Go to Step 12

4

  1. Turn ON the ignition, with the engine OFF.
  2. Test the positive battery voltage circuit of the exhaust solenoid valve with a test lamp that is connected to a good ground. Refer to Circuit Testing .

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 11

5

  1. Connect a test lamp between the control circuit of the exhaust solenoid valve and the positive battery voltage circuit of the exhaust solenoid valve, harness side. Refer to Circuit Testing .
  2. With a scan tool, clear all ALC DTCs.
  3. With a scan tool, command the exhaust ON and OFF .

Does the test lamp turn ON and OFF with each command?

--

Go to Step 9

Go to Step 6

6

Does the test lamp remain illuminated with each command?

--

Go to Step 8

Go to Step 7

7

Test the control circuit of the exhaust solenoid valve for a short to voltage and an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

8

Test the control circuit of the exhaust solenoid valve for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

9

Inspect for poor connections at the exhaust solenoid valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

10

Inspect for poor connections at the harness connector of the electronic suspension control (ESC) module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

11

Repair the positive battery voltage circuit of the exhaust solenoid valve. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 14

--

12

Replace the auto level control air compressor assembly. Refer to Air Compressor Replacement .

Did you complete the replacement?

--

Go to Step 14

--

13

Replace the suspension control module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 14

--

14
  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