DTC C0712 With F55

Diagnostic Instructions

DTC Descriptors

DTC C0712 01: Level Control Compressor Relay Circuit Short to Battery

DTC C0712 06: Level Control Compressor Relay Circuit Short to Ground or Open Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Automatic Level Control Relay Coil B+	C0712 06	C0712 06	--	--
Automatic Level Control Relay Coil Control	C0712 06	C0712 06	C0712 01	--

Circuit/System Description

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.

Conditions for Running the DTC

Conditions for Setting the DTC

Action Taken When the DTC Sets

Conditions for Clearing the DTC

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.

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

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

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.

Circuit/System Testing

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

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.

Repair Instructions

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.

DTC C0712 W/O F55

Diagnostic Instructions

DTC Descriptors

DTC C0712 01: Level Control Compressor Relay Circuit Short to Battery

DTC C0712 06: Level Control Compressor Relay Circuit Short to Ground or Open Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Automatic Level Control Relay Coil B+	C0712 06	C0712 06	--	--
Automatic Level Control Relay Coil Control	C0712 06	C0712 06	C0712 01	--

Circuit/System 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 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.

Conditions for Running the DTC

Conditions for Setting the DTC

Action Taken When the DTC Sets

The ALC system will be inoperative.

Conditions for Clearing the DTC

The ALC module 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 ALC module retries the output every 15 seconds to try to recover from the fault.

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

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

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.

Circuit/System Testing

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

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.

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.

Repair Instructions

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.