Rear of Vehicle High or Low
Rear of Vehicle High or Low
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The Automatic Level Control System uses the Suspension Control Module, level sensors, compressor, and exhaust valve to increase or decrease air pressure in the system to control trim height. Battery voltage is supplied to the exhaust valve and compressor relay. The Suspension Control Module controls the ground circuits that activate the exhaust valve and compressor relay which maintain trim height based on the level sensor input voltage.
Diagnostic Aids
* Trim Height Uneven or Low Trim Height Uneven or Low
* The Electronic Suspension Rear Position Sensor Trim Height Calibration Electronic Suspension Rear Position Sensor Trim Height Calibration procedure may correct the condition.
Reference Information
Schematic Reference
Electronic Suspension Control Schematics Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
Electronic Suspension Control Description and Operation Electronic Suspension Control
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, engine running.
2. Verify if the level control exhaust valve can be heard clicking when commanding the exhaust valve solenoid ON and OFF with a scan tool.
• If the level control exhaust valve cannot be heard clicking
1. Refer to Circuit/System Testing
• If the level control exhaust valve can be heard clicking
3. All OK
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF. It may take up to 2 min for all vehicle systems to power down.
2. Disconnect the harness connector at the G3 Air Suspension Compressor. Ignition ON.
3. Verify a test lamp illuminates between the B+ circuit terminal B at the harness connector and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF.
2. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the G3 Air Suspension Compressor.
• If the test lamp illuminates
4. Ignition OFF.
5. Test for less than 5 ohms between the ground circuit terminal G and ground.
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
6. Replace the G3 Air Suspension Compressor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Rear Air Spring Compressor Replacement Rear Air Spring Compressor Replacement
* Electronic Suspension Rear Position Sensor Trim Height Calibration Electronic Suspension Rear Position Sensor Trim Height Calibration
* Control Module References Control Module References for Suspension Control Module replacement, programming and setup