U0791 - Communication Error in the Vehicle Control Module (Common in 2015-2018 Chevrolet and GMC Models)

Quick Answer

U0791 means: U0791 indicates a communication failure between vehicle control modules.

Fix: Check and replace faulty components Cost: $100 - $300 Time: 90-180 minutes

Can I drive with U0791? Immediate attention is recommended to avoid further issues.

Common Questions

What does U0791 mean and how does it affect my car?

U0791 signifies a communication error between your vehicle's electronic control units. This can lead to performance issues such as hesitation during acceleration or irregularities in electronic systems. If ignored, it can escalate to more significant problems affecting your vehicle's reliability and safety.

What are the most common causes of U0791 and how much does it cost to fix?

Common causes of U0791 include faulty wiring (60% likelihood), malfunctioning ECM, and software issues. Repair costs range from $100 for wiring repairs to $1500 for ECM replacement, depending on the severity of the issue.

Can I drive my car with U0791 or should I stop immediately?

It's advisable to avoid driving your vehicle with an active U0791 code, as it can lead to further complications and safety risks. Seek immediate inspection to prevent exacerbating the issue.

How can I diagnose U0791 myself using GeekOBD APP?

You can use the GeekOBD APP to check for diagnostic trouble codes, review freeze frame data, and monitor real-time sensor data. This helps pinpoint the source of the communication failure.

What vehicles are most commonly affected by U0791?

U0791 is frequently seen in 2015-2018 Chevrolet and GMC models, including the Silverado and Sierra. Stay informed about any recalls or technical service bulletins related to these models.

How can I prevent U0791 from happening again?

To prevent U0791, maintain regular vehicle inspections, ensure proper wiring and connections, and keep your software updated. Consider periodic diagnostic scans with the GeekOBD APP to catch potential issues early.

What is U0791?

DTC U0791 indicates that there is a communication issue between the vehicle's control modules, most often affecting models like the Chevrolet Silverado and GMC Sierra from 2015 to 2018. This trouble code signals that one of the electronic control units (ECUs) is unable to properly communicate with others due to a malfunction or a connectivity issue. In practical terms, this can lead to a range of performance problems, including erratic engine behavior, potential loss of power steering, and issues with various electronic features in your vehicle. The underlying cause could be anything from wiring faults, software glitches, to failing control modules themselves. This problem can also trigger warning lights on your dashboard, including the check engine light, which may cause concern among drivers. Addressing this issue is critical, as it can affect the vehicle's overall reliability and safety. Regular maintenance checks and timely diagnostics can help catch these communication errors before they escalate into more serious problems, ensuring your vehicle remains safe and efficient on the road.

System: U - Network (Communication, CAN Bus)

Symptoms

Common symptoms when U0791 is present:

  • Check engine light stays on constantly, indicating a persistent issue that needs addressing.
  • Engine hesitates during acceleration, which can lead to unsafe driving conditions.
  • Fuel economy decreased by 10-15%, meaning you might be spending more on gas than necessary.
  • Inconsistent operation of electronic features, such as power windows or infotainment system.
  • Loss of power steering at times, which can significantly hinder vehicle handling and safety.

Possible Causes

Most common causes of U0791 (ordered by frequency):

  1. The most common cause is faulty wiring or connections, which accounts for about 60% of cases, often due to wear and tear or corrosion.
  2. A second common cause is a malfunctioning electronic control module (ECM), which can disrupt communication between components.
  3. Software glitches within the vehicle's systems can also lead to U0791; regular updates are essential to prevent this.
  4. Less common but serious causes include water intrusion into connectors, which can damage electronic components and cause failures.
  5. Rarely, a complete failure of the vehicle's main computer can result in this code, requiring a full replacement.

U0791 Repair Costs

Cost Breakdown by Repair Type

Wiring Repair

Repairing or replacing damaged wiring or connectors.

  • Total: $100 - $300
  • Success rate: 75%
ECM Replacement

Replacing a faulty electronic control module.

  • Total: $800 - $1500
  • Success rate: 90%
Software Update

Performing software updates to the vehicle's control modules.

  • Total: $50 - $150
  • Success rate: 80%
Money-Saving Tips for U0791
  • 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 U0791 Diagnosis Process

Follow these systematic steps to accurately diagnose U0791. 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 (5-10 minutes)

Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion (5-10 minutes).

GeekOBD APP Tip: Use GeekOBD APP to monitor real-time data during this diagnostic step for accurate results and professional-grade analysis.
Step 2: Step 2: OBD2 scan with GeekOBD APP - Retrieve all codes and freeze frame data to understand the fault context (10-15 minutes)

Step 2: OBD2 scan with GeekOBD APP - Retrieve all codes and freeze frame data to understand the fault context (10-15 minutes).

GeekOBD APP Tip: Use GeekOBD APP to monitor real-time data during this diagnostic step for accurate results and professional-grade analysis.
Step 3: Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components (20-30 minutes)

Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components (20-30 minutes).

GeekOBD APP Tip: Use GeekOBD APP to monitor real-time data during this diagnostic step for accurate results and professional-grade analysis.
Step 4: Step 4: System function test - Verify proper operation after repairs and clear codes (10-15 minutes)

Step 4: System function test - Verify proper operation after repairs and clear codes (10-15 minutes).

GeekOBD APP Tip: Use GeekOBD APP to monitor real-time data during this diagnostic step for accurate results and professional-grade analysis.
Step 5: Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success (15-20 minutes)

Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success (15-20 minutes).

GeekOBD APP Tip: Use GeekOBD APP to monitor real-time data during this diagnostic step for accurate results and professional-grade analysis.

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: 2016 Chevrolet Silverado U0791 Repair

Vehicle: 2016 Chevrolet Silverado, 75,000 miles

Problem: Customer reported check engine light and engine hesitation.

Diagnosis: Visual inspection revealed corroded wiring in the ECM harness.

Solution: Replaced damaged wiring and performed a software update.

Cost: $200 (including parts and labor)

Result: Check engine light cleared and engine performance restored.

Case Study 2: 2017 GMC Sierra U0791 Issue

Vehicle: 2017 GMC Sierra, 50,000 miles

Problem: Intermittent power steering loss and dashboard warning lights.

Diagnosis: Diagnostic scan confirmed U0791; further inspection showed a malfunctioning ECM.

Solution: Replaced the ECM and reprogrammed the vehicle.

Cost: $1200 (for parts and labor)

Result: All systems functioning normally after repair.

Diagnose U0791

Use GeekOBD APP for professional diagnosis!

  • Real-time data monitoring
  • Advanced diagnostic features
  • Step-by-step repair guidance
  • Professional-grade analysis
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Code Information

Code: U0791
System: Network (Communication, CAN Bus)
Severity: HIGH
Category: Network Codes