Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 2: Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
- 3: Check for the presence of DTCs.
- 4: The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
- 5: Check for the presence of DTCs in Body Control system.
- 6: Check for the presence of DTCs in Automatic Level Control system.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Automatic Level Control Suspension Schematics | |||
| 1 | Install a scan tool. Does the scan tool power up? | Go to Step 2 | Go to SCAN TOOL DOES NOT POWER UP in Data Link Communications |
| 2 | Turn ON the ignition, with the engine OFF. Attempt to establish communication with the suspension control module. Does the scan tool communicate with the suspension control module? | Go to Step 3 | Go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in Data Link Communications |
| 3 | Select the suspension control module display DTCs function on the scan tool. Does the scan tool display any DTCs? | Go to Step 4 | Go to Symptoms - Automatic Level Control |
| 4 | Does the scan tool display any DTCs which begin with a "U"? | Go to SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in Data Link Communications | Go to Step 5 |
| 5 | Does the scan tool display DTC B1000? | Go to DIAGNOSTIC TROUBLE CODE (DTC) LIST in Body Control System | Go to Step 6 |
| 6 | Does the scan tool display DTC C0655, C0660, or C0711? | Go to Diagnostic Trouble Code (DTC) List | Go to DIAGNOSTIC TROUBLE CODE (DTC) LIST in Real Time Damping |
Diagnostic System Check - Automatic Level Control
The numbers below refer to the step numbers on the diagnostic table.
- 2: Command both the ON and OFF states. Repeat the commands as necessary.
- 3: Tests the coil of the relay for continuity.
- 4: Tests for voltage at the coil side of the compressor motor relay. The IGN 3 fuse supplies power to the coil side of the compressor motor relay.
- 5: Verifies that the Suspension Control module is providing ground to the compressor motor relay.
- 6: Tests if ground is constantly being applied to the compressor motor relay.
- 7: Test for a short to voltage or an open in the control circuit of the compressor motor relay.
- 13: The replacement Suspension Control module must be calibrated.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Automatic Level Control Suspension Schematics | ||||
| 1 | Did you perform the Automatic Level control Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Automatic Level Control | |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the compressor ON and OFF. Does the compressor turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 3 | |
| 3 | Turn OFF the ignition. Disconnect the compressor motor relay. Measure the resistance of the relay coil. Does the resistance measure within the specified value? | 30-90 ohms | Go to Step 4 | Go to Step 12 |
| 4 | Turn ON the ignition, with the engine OFF. Probe the coil side feed circuit of the compressor motor relay with a test lamp that is connected to a good ground. Refer to CIRCUIT TESTING in Wiring Systems. Does the test lamp illuminate? | Go to Step 5 | Go to Step 11 | |
| 5 | Connect a test lamp between the control circuit of the compressor motor relay and the coil side feed circuit of the compressor motor relay. Refer to CIRCUIT TESTING in Wiring Systems. With a scan tool, command the compressor 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 compressor motor relay for a short to voltage and an open. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 10 | |
| 8 | Test the control circuit of the compressor motor relay for a short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 10 | |
| 9 | Inspect for poor connections at the compressor motor relay. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems. 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 Suspension Control module. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 13 | |
| 11 | Repair the coil side feed circuit of the compressor motor relay. Refer to WIRING REPAIRS in Wiring Systems. Did you complete the repair? | Go to Step 14 | ||
| 12 | Replace the compressor motor relay. Did you complete the replacement? | Go to Step 14 | ||
| 13 | IMPORTANT: After replacement, use the scan tool to perform the calibration procedure for the Suspension Control module, located under Special Functions: Recalibration. Replace the Suspension Control module. Refer to ELECTRONIC SUSPENSION CONTROL MODULE REPLACEMENT (TAHOE/YUKON/ESCALADE) or ELECTRONIC SUSPENSION CONTROL MODULE REPLACEMENT (ESCALADE EXT) .Did you complete the replacement? | Go to Step 14 | ||
| 14 | Use the scan tool in order to clear the DTCs. 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 | |
| IMPORTANT |
|---|
| After replacement, use the scan tool to perform the calibration procedure for the Suspension Control module, located under Special Functions: Recalibration. |
DTC C0655
The numbers below refer to the step numbers on the diagnostic table.
- 2: Command both the ON and OFF states. Repeat the commands as necessary.
- 3: Test the exhaust solenoid valve resistance.
- 4: 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.
- 5: Verifies that the Suspension Control module is providing ground to the exhaust solenoid valve.
- 6: Tests if ground is constantly being applied to the exhaust solenoid valve.
- 7: Test the control circuit of the exhaust solenoid valve for a short to voltage and an open.
- 13: The replacement Suspension Control module must be calibrated.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Automatic Level Control Suspension Schematics | ||||
| 1 | Did you perform the Automatic Level Control Diagnostic System Check? | Go to Step 2 | Go to Diagnostic System Check - Automatic Level Control | |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. 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 | Turn OFF the ignition. Disconnect the compressor leveling module connector. Measure the resistance from the positive battery voltage circuit of the exhaust solenoid valve and the control circuit of the exhaust solenoid valve. Does the resistance measure within the specified value? | 30-90 ohms | Go to Step 4 | Go to Step 12 |
| 4 | Turn ON the ignition, with the engine OFF. Probe 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 in Wiring Systems. Does the test lamp illuminate? | Go to Step 5 | Go to Step 11 | |
| 5 | 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 in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. 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 AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems. 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 ESC module. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems. 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 in Wiring Systems. Did you complete the repair? | Go to Step 14 | ||
| 12 | Replace the exhaust solenoid valve. Did you complete the replacement? | Go to Step 14 | ||
| 13 | IMPORTANT: After replacement, use the scan tool to perform the calibration procedure for the Suspension Control module, located under Special Functions: Recalibration. Replace the Suspension Control module. Refer to ELECTRONIC SUSPENSION CONTROL MODULE REPLACEMENT (TAHOE/YUKON/ESCALADE) or ELECTRONIC SUSPENSION CONTROL MODULE REPLACEMENT (ESCALADE EXT) .Did you complete the replacement? | Go to Step 14 | ||
| 14 | Use the scan tool in order to clear the DTCs. 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 | |
| IMPORTANT |
|---|
| After replacement, use the scan tool to perform the calibration procedure for the Suspension Control module, located under Special Functions: Recalibration. |
DTC C0660
The numbers below refer to the step numbers on the diagnostic table.
- 2: Tests for a high resistance or an open in the ground circuit.
- 7: Check for open or high resistance in the sensor ground circuit.
- 13: The replacement suspension control module must be calibrated.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference | ||||
| 1 | IMPORTANT: If DTC C0870 is present, perform the diagnosis for DTC C0870 first. Did you perform the Automatic Level Control Diagnostic System Check? | Go to Step 2 | Go to | |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. With the scan tool, observe the Air Pressure Sensor data parameter in the ALC data list. Does the scan tool indicate that the Air Pressure Sensor parameter is within the specified range? | 0.15 - 4.85 V | Go to in Wiring Systems. | Go to Step 3 |
| 3 | Turn OFF the ignition. Disconnect the ALC compressor connector. Turn ON the ignition, with the engine OFF. With the scan tool, observe the air pressure sensor data parameter. Does the scan tool indicate that the air pressure sensor data parameter is at the specified value? | 0.0 V | Go to Step 4 | Go to Step 6 |
| 4 | Connect a 3 amp fused jumper wire between the 5 volt reference and signal circuit of the ALC compressor harness connector. Does the scan tool indicate that the Air Pressure Sensor data parameter is within the specified range? | 4.8-5.2 V | Go to Step 9 | Go to Step 5 |
| 5 | Test the pressure sensor signal circuit for an open, or short to ground. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 6 | |
| 6 | Test the pressure sensor signal circuit for a short to voltage. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 7 | |
| 7 | Test the pressure sensor 5 volt reference circuit an open, or short to ground. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 8 | |
| 8 | Test the pressure sensor 5 volt reference circuit for a short to voltage. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 10 | |
| 9 | Test the pressure sensor low reference circuit for an open, or short to voltage. Did you find and correct the condition? | Go to Step 14 | Go to Step 12 | |
| 10 | Inspect for poor connections at the ALC compressor harness connector. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 11 | |
| 11 | Inspect for poor connections at the suspension control module harness connector. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 14 | Go to Step 13 | |
| 12 | Replace the pressure sensor. Refer to in Automatic Level Control. Did you complete the replacement? | Go to Step 14 | ||
| 13 | IMPORTANT: After replacement, use the scan tool to perform the calibration procedure for the suspension control module, located under Special Functions: Recalibration. Replace the suspension control module. Refer to in Electronic Suspension Control (ESC).Did you complete the replacement? | Go to Step 14 | ||
| 14 | Use the scan tool in order to clear the DTCs. 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 | |
| IMPORTANT |
|---|
| If DTC C0870 is present, perform the diagnosis for DTC C0870 first. |
| IMPORTANT |
|---|
| After replacement, use the scan tool to perform the calibration procedure for the suspension control module, located under Special Functions: Recalibration. |
DTC C0711
Symptoms - Automatic Level Control
| IMPORTANT | The following steps must be completed before using the symptom tables. Perform the Automatic Level Control Diagnostic System Check before using the symptom table in order to verify that all of the following are true: There are no DTCs set. The control modules can communicate via the serial data link. Review the system operation in order to familiarize yourself with the system functions. Refer to Automatic Level Control Description and Operation . |
Automatic Level Control Description and Operation
The RTD system is bi-state real time damping system. The Suspension Control module controls the suspension damper solenoids and suspension position sensors, along with parts of the automatic level control (ALC) system and electronic variable orifice (EVO) power steering system.
The Automatic Level Control system consists of the following
- Suspension Control Module
- Compressor/Leveling Module Air Pressure Sensor Exhaust Solenoid
- Compressor Motor Relay
The objective of the Automatic Level Control System is to provide constant ride height at all load conditions. The Suspension Control module monitors body-to-wheel height, and vehicle speed.
The Suspension Control module will use the rear body-to-wheel displacements and vehicle speed inputs to keep the rear trim height of the vehicle at its desired level.