U091C - Understanding DTC U091C: Common Issues in 2015-2018 GM Vehicles

Quick Answer

U091C means: DTC U091C refers to a communication issue within the vehicle's CAN bus system, affecting module connectivity.

Fix: Check and replace faulty components Cost: $150 - $300 Time: 90-180 minutes

Can I drive with U091C? Immediate attention is advised to prevent further complications.

Common Questions

What does U091C mean and how does it affect my car?

DTC U091C signifies a communication error in the vehicle's network, impacting various systems like the engine and safety features. If left unaddressed, this could lead to performance issues and potential safety risks, as critical systems may not function correctly.

What are the most common causes of U091C and how much does it cost to fix?

Common causes include damaged wiring, faulty control modules, or software glitches, with repair costs ranging from $100 for software updates to $1,000 for module replacements. Regular inspections can help mitigate these issues.

Can I drive my car with U091C or should I stop immediately?

While you might be able to drive the car, it's best to avoid doing so until the issue is resolved. Ignoring DTC U091C can lead to more severe problems, including safety hazards.

How can I diagnose U091C myself using GeekOBD APP?

Using the GeekOBD APP, start by scanning your vehicle for trouble codes. Analyze the freeze frame data to understand the conditions under which the code appeared. Check for any additional codes that could provide clues about the underlying issue.

What vehicles are most commonly affected by U091C?

U091C is frequently encountered in 2015-2018 Chevrolet and GMC models, including the Silverado, Sierra, and Equinox. Be sure to check for any known recalls or technical service bulletins (TSBs) related to your specific model.

How can I prevent U091C from happening again?

To prevent U091C, regularly inspect the vehicle's wiring and connectors, especially if the vehicle is exposed to harsh conditions. Keeping software updated and avoiding aftermarket modifications can also help maintain communication integrity.

What is U091C?

The diagnostic trouble code (DTC) U091C indicates a communication issue in the vehicle's network, specifically related to the controller area network (CAN) bus system. This code typically arises when one or more control modules in the vehicle are unable to communicate effectively with each other. In practical terms, this could lead to various electrical or performance issues, as the modules rely on seamless communication to operate correctly. For example, if your 2016 Chevrolet Silverado throws this code, you might notice that features like the anti-lock braking system (ABS) or traction control are not functioning properly. It's essential to address this issue promptly, as prolonged communication failures may lead to further electrical malfunctions or even safety concerns. The underlying cause can stem from damaged wiring, faulty connectors, or even software glitches within the control modules. Understanding the implications of DTC U091C can help vehicle owners take appropriate action to ensure their vehicle remains safe and operational.

System: U - Network (Communication, CAN Bus)

Symptoms

Common symptoms when U091C is present:

  • The check engine light illuminates and remains on, indicating a persistent issue that needs addressing.
  • You may experience erratic behavior in vehicle systems, such as unexpected power loss or failure of features like cruise control.
  • Your vehicle's fuel economy may drop significantly, sometimes by 10-15%, due to inefficient module communication affecting engine performance.
  • The ABS or traction control warning lights may activate, signaling potential safety concerns.
  • In some cases, the vehicle may enter 'limp mode,' restricting performance to prevent further damage.

Possible Causes

Most common causes of U091C (ordered by frequency):

  1. The most common cause is damaged wiring or loose connections in the CAN bus system, which occurs in about 50% of cases. Regular maintenance can prevent corrosion and damage.
  2. The second most frequent cause is faulty control modules, which can stem from manufacturing defects or age-related wear. Ensure to check for any recalls on your vehicle.
  3. Another possible cause is software glitches in the modules, which can often be resolved with a simple software update at a dealership.
  4. A less common but serious cause includes water intrusion in connectors or modules, especially in vehicles exposed to heavy rain or flooding.
  5. Rarely, issues may arise from aftermarket modifications, which can interfere with the communication between factory-installed modules.

U091C Repair Costs

Cost Breakdown by Repair Type

Wiring Repair

Repairing damaged wiring or connections in the CAN bus system.

  • Total: $150 - $300
  • Success rate: 85%
Control Module Replacement

Replacing faulty control modules that are no longer communicating effectively.

  • Total: $500 - $1,000
  • Success rate: 90%
Software Update

Performing a software update to resolve glitches in communication.

  • Total: $100 - $200
  • Success rate: 75%
Money-Saving Tips for U091C
  • 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 U091C Diagnosis Process

Follow these systematic steps to accurately diagnose U091C. 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, ensuring all modules are powered correctly (20-30 minutes)

Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components, ensuring all modules are powered correctly (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 to ensure the issue has been resolved (10-15 minutes)

Step 4: System function test - Verify proper operation after repairs and clear codes to ensure the issue has been resolved (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 and check for any reoccurrence of the code (15-20 minutes)

Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success and check for any reoccurrence of the code (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 - Communication Failure

Vehicle: 2016 Chevrolet Silverado, 75,000 miles

Problem: Customer reported check engine light and erratic ABS system.

Diagnosis: After scanning with GeekOBD APP, U091C was identified. Visual inspection revealed corroded wiring in the CAN bus system.

Solution: Repaired the damaged wiring and replaced connectors.

Cost: $250

Result: The check engine light turned off, and ABS functionality was restored.

Case Study 2: 2017 GMC Sierra - Module Replacement

Vehicle: 2017 GMC Sierra, 60,000 miles

Problem: Customer experienced cruise control failure and intermittent check engine light.

Diagnosis: Diagnosis revealed U091C and further testing indicated a faulty control module.

Solution: Replaced the faulty control module.

Cost: $750

Result: All systems were restored to normal functionality, and no codes reappeared after testing.

Diagnose U091C

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: U091C
System: Network (Communication, CAN Bus)
Severity: HIGH
Category: Network Codes