The AWD system in your 2020 Buick Envision provides confidence in varying conditions—until a warning message announces "AWD System Malfunction" and that confidence evaporates. Understanding how the system works and what causes failures helps you assess the severity and plan repairs.
How the Envision's AWD Works
The Envision uses an on-demand AWD system with an electronically controlled rear drive module (RDM). Under normal conditions, the vehicle operates primarily as front-wheel drive. When sensors detect wheel slip or the system predicts the need for additional traction, the RDM clutch pack engages to send power to the rear wheels.
Common Warning Messages
- "AWD System Malfunction"
- "Service AWD System"
- "AWD Off" or AWD indicator flashing
- Traction control warning accompanying AWD message
Common Causes
Rear Drive Module (RDM) Failure
The RDM contains the clutch pack and electronics that control rear axle engagement. Overheating, clutch wear, or electronic failure can disable the system.
Fluid Problems
The RDM requires specific fluid for cooling and lubrication. Low fluid from leaks, contaminated fluid, or wrong fluid type causes operational problems.
Sensor Failures
The system relies on wheel speed sensors, steering angle sensor, and other inputs. Failed sensors can cause the system to disable as a precaution.
Wiring and Connector Issues
The rear drive module connector or wiring can develop problems from road debris damage, corrosion, or poor connections.
Software Glitches
The control module software can experience glitches requiring updates or resets.
Diagnostic Approach
- Scan for codes: The AWD control module stores diagnostic codes identifying specific failures.
- Check fluid: Verify RDM fluid level and condition if there's a check point.
- Sensor verification: Ensure all wheel speed sensors are functioning properly.
- Wiring inspection: Check connectors and wiring at the rear drive module for damage.
- Software check: Verify system software is current version.
Driving Without AWD
When the AWD system malfunctions, the Envision typically defaults to front-wheel drive. The vehicle remains safe to drive but:
- You lose all-weather traction advantages
- Performance in rain, snow, or slippery conditions is reduced
- The vehicle handles like a standard FWD
Repair Costs
- Diagnostic scan: $75-$150
- Sensor replacement: $150-$400
- RDM fluid service: $100-$200
- Wiring repair: $150-$400
- RDM clutch pack service: $800-$1,500
- Complete RDM replacement: $1,500-$3,000