Quick Answer
C0639 means: C0639 indicates a performance issue with the Power Steering Control Module, affecting steering assist.
Can I drive with C0639? Immediate attention is recommended to ensure safe driving conditions.
Common Questions
What does C0639 mean and how does it affect my car?
DTC C0639 indicates a performance issue with the Power Steering Control Module, which can significantly affect your vehicle's steering responsiveness and safety. If you notice heavy steering or warning lights, it's crucial to address the issue immediately to avoid further complications.
What are the most common causes of C0639 and how much does it cost to fix?
The most common causes include a failing Power Steering Control Module, wiring issues, or low power steering fluid. Repair costs can range from $150 for wiring repairs up to $800 for module replacement, depending on the specific problem.
Can I drive my car with C0639 or should I stop immediately?
It is not advisable to drive your vehicle with the C0639 code present, as it can lead to unsafe steering conditions. If you experience heavy steering or warning lights, it's best to stop driving and have it inspected.
How can I diagnose C0639 myself using GeekOBD APP?
Using the GeekOBD APP, you can scan your vehicle for trouble codes and freeze frame data. Focus on any power steering-related codes and monitor the live data to check for abnormal readings, which can help pinpoint the issue.
What vehicles are most commonly affected by C0639?
C0639 is most commonly seen in 2015-2020 Chevrolet Silverado, GMC Sierra, and other GM vehicles that utilize the electric power steering system. Always check for any manufacturer recalls or TSBs related to your specific model.
How can I prevent C0639 from happening again?
Regular maintenance, including checking power steering fluid levels, inspecting wiring and connectors, and keeping the steering system clean and free of debris, can help prevent future occurrences of the C0639 code.
What is C0639?
DTC C0639 indicates a problem with the Power Steering Control Module (PSCM) in certain Chevrolet and GMC vehicles, particularly from the 2015 to 2020 model years. This code is triggered when the module detects that the steering assist is either too high or too low, which can lead to difficult steering or a complete loss of power steering assistance. In real-world terms, this means that drivers may experience an increased effort when turning the steering wheel, especially at low speeds, or the steering may feel unresponsive. The PSCM is responsible for monitoring and controlling the electric power steering system. When it detects discrepancies in performance, it sets the C0639 code to alert the driver and the technician to a potential issue. If left unaddressed, this can lead to more severe steering problems, increased wear on components, and could potentially compromise safety while driving. Understanding this code is essential for maintaining your vehicle's drivability and safety, making timely repairs necessary to avoid escalating issues.
System: C - Chassis (ABS, Steering, Suspension)
Symptoms
Common symptoms when C0639 is present:
- The steering wheel becomes heavy or difficult to turn, especially at slow speeds, making it challenging to maneuver in parking lots.
- The power steering warning light appears on the dashboard, indicating an issue with the system that requires immediate attention.
- The vehicle may experience sudden jerks or unresponsiveness in steering, leading to potential safety hazards while driving.
- You might notice unusual noises, like whining or grinding, when turning the steering wheel, indicating underlying mechanical issues.
- There may be a noticeable difference in steering feel, with the steering feeling loose or overly tight at times.
Possible Causes
Most common causes of C0639 (ordered by frequency):
- The most common cause of C0639 is a failure in the Power Steering Control Module, which occurs in about 60% of cases. This can be due to electrical issues, software glitches, or internal module failures.
- Another likely cause is wiring problems, such as damaged or corroded connectors, which can disrupt communication between the PSCM and the steering system, accounting for around 25% of instances.
- Low power steering fluid levels or fluid contamination can lead to inadequate steering assist, representing about 10% of cases. Regular maintenance checks can help prevent this.
- Less commonly, a malfunctioning steering angle sensor may send incorrect data to the PSCM, resulting in the C0639 code being set.
- In rare cases, issues with the vehicle's battery or charging system can affect the PSCM's operation, although this is less frequently encountered.
C0639 Repair Costs
Cost Breakdown by Repair Type
Power Steering Control Module Replacement
Replacing the faulty Power Steering Control Module with a new or refurbished unit.
- Total: $400 - $800
- Success rate: 85%
Wiring and Connector Repair
Repairing or replacing damaged wiring and connectors associated with the power steering system.
- Total: $150 - $300
- Success rate: 75%
Steering Angle Sensor Replacement
Replacing a faulty steering angle sensor that may be contributing to the issue.
- Total: $200 - $400
- Success rate: 70%
Money-Saving Tips for C0639
- Start with the most common and least expensive repairs first
- Use GeekOBD APP to confirm diagnosis before replacing expensive parts
- Consider preventive maintenance to avoid future occurrences
- Compare prices for OEM vs aftermarket parts based on your needs
- Address the issue promptly to prevent more expensive secondary damage
Diagnostic Steps
Professional C0639 Diagnosis Process
Follow these systematic steps to accurately diagnose C0639. Each step builds on the previous one to ensure accurate diagnosis.
Step 1: Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion, which may take around 5-10 minutes
Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion, which may take around 5-10 minutes.
Step 2: Step 2: OBD2 scan with GeekOBD APP - Use the app to retrieve all codes and freeze frame data to understand the fault context, which usually takes 10-15 minutes
Step 2: OBD2 scan with GeekOBD APP - Use the app to retrieve all codes and freeze frame data to understand the fault context, which usually takes 10-15 minutes.
Step 3: Step 3: Component testing - Utilize a multimeter or specific diagnostic tools to test the Power Steering Control Module and related components for proper operation, estimated time: 20-30 minutes
Step 3: Component testing - Utilize a multimeter or specific diagnostic tools to test the Power Steering Control Module and related components for proper operation, estimated time: 20-30 minutes.
Step 4: Step 4: System function test - After repairs, verify the proper operation of the power steering system and clear the codes, typically taking 10-15 minutes
Step 4: System function test - After repairs, verify the proper operation of the power steering system and clear the codes, typically taking 10-15 minutes.
Step 5: Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success, which typically lasts 15-20 minutes
Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success, which typically lasts 15-20 minutes.
Important Notes
- Always verify the repair with GeekOBD APP after completing diagnostic steps
- Clear codes and test drive to ensure the problem is resolved
- Address underlying causes to prevent code recurrence
Real Repair Case Studies
Case Study 1: Power Steering Control Module Replacement for 2016 Chevrolet Silverado 1500
Vehicle: 2016 Chevrolet Silverado 1500, 75,000 miles
Problem: Customer reported heavy steering and power steering warning light illuminated.
Diagnosis: Diagnostic scan revealed C0639 code. Visual inspection indicated corrosion in the connections leading to the PSCM.
Solution: Replaced the Power Steering Control Module and repaired corroded wiring.
Cost: $550 (including parts and labor)
Result: Customer reported significant improvement in steering feel and no warning lights after the repair.
Case Study 2: Wiring Repair on 2018 GMC Sierra 2500HD
Vehicle: 2018 GMC Sierra 2500HD, 60,000 miles
Problem: Customer experienced erratic steering assist and power steering warning light on dashboard.
Diagnosis: C0639 code confirmed; detailed inspection found damaged wiring harness near the steering column.
Solution: Repaired damaged wiring and reconnected the PSCM.
Cost: $200 (including parts and labor)
Result: Post-repair, the vehicle had normal steering operation and no further issues.