Quick Answer
U0956 means: U0956 signifies a communication error between vehicle control modules.
Can I drive with U0956? Immediate diagnosis and repair are recommended to avoid further vehicle issues.
Common Questions
What does U0956 mean and how does it affect my car?
U0956 indicates a communication error between control modules, potentially affecting your car's performance and safety features. If ignored, this can lead to poor engine efficiency or even driveability issues.
What are the most common causes of U0956 and how much does it cost to fix?
Common causes include wiring issues, faulty modules, or software glitches. Repair costs can range from $150 for wiring repairs to over $1200 for module replacements, depending on the severity of the problem.
Can I drive my car with U0956 or should I stop immediately?
While it may be possible to drive your car with U0956, it is not advisable. The communication error can lead to erratic vehicle behavior, and it’s best to seek repairs as soon as possible.
How can I diagnose U0956 myself using GeekOBD APP?
Using the GeekOBD APP, connect to your vehicle’s OBD2 port, scan for codes, and examine freeze frame data to understand when the problem occurs. This helps you pinpoint potential issues before visiting a professional.
What vehicles are most commonly affected by U0956?
U0956 frequently appears in 2015-2020 Chevrolet and GMC vehicles, including models like the Silverado, Sierra, and Equinox. Keep an eye on any recalls or technical service bulletins related to these models.
How can I prevent U0956 from happening again?
Regular maintenance, including wiring inspections and software updates, can help prevent U0956. Ensure your vehicle’s electrical system is in good shape to minimize risks.
What is U0956?
The diagnostic trouble code (DTC) U0956 indicates a communication error between the vehicle's control modules, particularly in General Motors (GM) vehicles like Chevrolet and GMC from 2015 to 2020. This code arises when one module, such as the transmission control module (TCM) or body control module (BCM), fails to communicate with another module over the Controller Area Network (CAN) bus. This situation can lead to various performance issues, as multiple systems rely on seamless communication for proper vehicle operation. For instance, if the TCM cannot relay information about gear shifting, drivers may experience erratic shifting or even complete transmission failure in severe cases. The symptoms of U0956 can range from a simple warning light on the dashboard to more significant issues affecting engine performance, fuel efficiency, and safety features like ABS and traction control. Ignoring this code can lead to increased repair costs over time, as the underlying issues may worsen without prompt attention. Therefore, understanding U0956 is crucial for ensuring your vehicle operates smoothly and safely.
System: U - Network (Communication, CAN Bus)
Symptoms
Common symptoms when U0956 is present:
- The check engine light remains illuminated, indicating a persistent issue that requires attention.
- Engine performance may become sluggish, with noticeable delays in acceleration or shifting, creating a frustrating driving experience.
- Fuel economy could decrease by 10-20%, as the engine management system struggles to optimize performance without accurate data from other modules.
- Unresponsive electronic features like power windows or locks may occur, suggesting deeper issues in the vehicle's electrical system.
- In some cases, the vehicle may enter 'limp mode,' whereby it restricts power to protect the engine and transmission, making it difficult to drive.
Possible Causes
Most common causes of U0956 (ordered by frequency):
- Wiring issues or poor connections are the most common cause of U0956, accounting for about 40% of cases. Corrosion or damage can disrupt the CAN bus signals.
- Faulty control modules, such as a malfunctioning TCM or BCM, can also trigger this code. These components may require replacement if diagnosed correctly.
- Software glitches in the vehicle’s control systems can lead to communication errors. Keeping the software updated is crucial for optimum performance.
- Less common causes include short circuits in the wiring harness, which can create intermittent connectivity issues and lead to the DTC appearing sporadically.
- In rare cases, a failed battery or charging system can result in low voltage scenarios, affecting module communication and causing U0956.
U0956 Repair Costs
Cost Breakdown by Repair Type
Wiring Repair or Replacement
Fixing or replacing damaged wiring or connectors in the CAN bus system.
- Total: $150 - $500
- Success rate: 90%
Control Module Replacement
Replacing a faulty TCM or BCM that is not communicating properly.
- Total: $500 - $1200
- Success rate: 85%
Software Update
Updating the vehicle's software to fix glitches causing communication failure.
- Total: $50 - $150
- Success rate: 70%
Money-Saving Tips for U0956
- 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 U0956 Diagnosis Process
Follow these systematic steps to accurately diagnose U0956. Each step builds on the previous one to ensure accurate diagnosis.
Step 1: Step 1: Conduct an initial visual inspection of the vehicle's wiring and connectors, looking for any obvious damage or corrosion that could lead to communication failures (5-10 minutes)
Step 1: Conduct an initial visual inspection of the vehicle's wiring and connectors, looking for any obvious damage or corrosion that could lead to communication failures (5-10 minutes).
Step 2: Step 2: Use an OBD2 scanner with the GeekOBD APP to retrieve all stored codes and freeze frame data
Step 2: Use an OBD2 scanner with the GeekOBD APP to retrieve all stored codes and freeze frame data. This provides context for the U0956 code and any related codes (10-15 minutes).
Step 3: Step 3: Perform component testing on suspected faulty modules using a multimeter or specialized diagnostic tools to assess their functionality (20-30 minutes)
Step 3: Perform component testing on suspected faulty modules using a multimeter or specialized diagnostic tools to assess their functionality (20-30 minutes).
Step 4: Step 4: After repairs, conduct a system function test to ensure all modules are communicating correctly, and clear any DTCs from the memory (10-15 minutes)
Step 4: After repairs, conduct a system function test to ensure all modules are communicating correctly, and clear any DTCs from the memory (10-15 minutes).
Step 5: Step 5: Finally, perform a road test to verify the vehicle's performance under various driving conditions, ensuring that the issue has been resolved (15-20 minutes)
Step 5: Finally, perform a road test to verify the vehicle's performance under various driving conditions, ensuring that the issue has been resolved (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: Chevrolet Silverado U0956 Diagnosis and Repair
Vehicle: 2018 Chevrolet Silverado, 45,000 miles
Problem: Customer reported check engine light and erratic shifting.
Diagnosis: Initial inspection showed corroded connectors in the CAN bus. OBD2 scanning revealed U0956 and associated codes.
Solution: Replaced corroded connectors and performed a software update to ensure proper communication.
Cost: $350 (including parts and labor)
Result: Post-repair, the vehicle shifted smoothly, and the check engine light was cleared.
Case Study 2: GMC Terrain U0956 Troubleshooting
Vehicle: 2017 GMC Terrain, 60,000 miles
Problem: Customer experienced poor fuel economy and a persistent check engine light.
Diagnosis: Diagnostic tests confirmed U0956 due to a faulty TCM. A multimeter test indicated output failure from the module.
Solution: Replaced the TCM and reprogrammed it to the vehicle.
Cost: $900 (including parts and labor)
Result: The vehicle's fuel efficiency improved, and the check engine light remained off after repairs.