U0938 - Understanding DTC U0938: Common Issues in 2015-2018 Chevrolet Silverado and GMC Sierra

Quick Answer

U0938 means: U0938 indicates a lost communication with the trailer brake control module, affecting towing safety.

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

Can I drive with U0938? Immediate attention is recommended to avoid potential towing hazards.

Common Questions

What does U0938 mean and how does it affect my car?

The U0938 code indicates a lost connection with the trailer brake control module. This can significantly affect your vehicle's ability to brake effectively while towing, potentially leading to dangerous situations. It's essential to address this issue promptly to maintain safe towing operations.

What are the most common causes of U0938 and how much does it cost to fix?

Common causes include faulty wiring (60% likelihood), malfunctioning brake control modules (25%), and poor grounding. Repair costs can range from $100 to $600 depending on the specific issue and parts needed.

Can I drive my car with U0938 or should I stop immediately?

It's advisable to stop driving your vehicle if you see the U0938 code, especially when towing. The loss of communication with the trailer brake system can lead to unsafe braking, which poses a risk to you and other road users.

How can I diagnose U0938 myself using GeekOBD APP?

By using the GeekOBD APP, you can easily scan for diagnostic codes and view freeze frame data. Look for any additional codes that may appear alongside U0938, as they can offer more context on the issue. Additionally, check wiring and connections visually.

What vehicles are most commonly affected by U0938?

The U0938 code frequently appears in models like the 2015-2018 Chevrolet Silverado and GMC Sierra. Always check for any recalls or service bulletins related to your vehicle model.

How can I prevent U0938 from happening again?

Regularly inspect the wiring and connectors for wear, ensure that all connections are secure, and maintain proper grounding in your towing system to prevent communication loss.

What is U0938?

The diagnostic trouble code U0938 indicates a 'Lost Communication with Trailer Brake Control Module.' This code typically surfaces in vehicles equipped with a trailer brake control system, such as the 2015-2018 Chevrolet Silverado and GMC Sierra models. When this code is triggered, it signifies that the vehicle's onboard communication system has lost contact with the trailer brake control module, which is essential for maintaining proper braking performance when towing. The implications can be significant; if the module is not functioning correctly, the vehicle may struggle to properly manage braking while towing, leading to potentially dangerous driving conditions. This issue can arise from various sources, including wiring problems, faulty connectors, or a malfunctioning control module. Recognizing this code early can help prevent further damage to the electrical system and ensure safe towing operations. Car owners should take this code seriously, as ignoring it may lead to increased repair costs and compromised vehicle performance.

System: U - Network (Communication, CAN Bus)

Symptoms

Common symptoms when U0938 is present:

  • The check engine light remains illuminated, signaling an issue that requires immediate attention.
  • You may notice that the trailer brakes are not responding as expected, leading to jerky stops or increased stopping distances.
  • Fuel economy may decrease, especially when towing, as the vehicle's systems are overloaded trying to compensate for the communication loss.
  • Increased brake wear can occur due to improper braking response, leading to more frequent brake replacements.
  • Potential electrical issues may arise, causing other systems in the vehicle to malfunction.

Possible Causes

Most common causes of U0938 (ordered by frequency):

  1. The most common cause of U0938 is a faulty or disconnected wiring harness, which has a likelihood of about 60%. This could be due to wear and tear or rust affecting the connections.
  2. Another potential cause is a malfunctioning trailer brake control module, which can occur due to internal component failure, leading to a 25% chance of this being the issue.
  3. Poor grounding in the towing system can also lead to communication loss, which is preventable by regularly checking and maintaining connections.
  4. Less common but serious causes include water intrusion into the electronic modules, which can lead to corrosion and systemic failures.
  5. A rare cause could be software issues in the vehicle's ECU, requiring a dealer update to resolve.

U0938 Repair Costs

Cost Breakdown by Repair Type

Wiring Harness Repair

Repair or replace damaged wiring and connectors associated with the trailer brake control module.

  • Total: $100 - $300
  • Success rate: 85%
Trailer Brake Control Module Replacement

Replacing a faulty trailer brake control module if the diagnostics indicate it is not functioning.

  • Total: $300 - $600
  • Success rate: 90%
Money-Saving Tips for U0938
  • 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 U0938 Diagnosis Process

Follow these systematic steps to accurately diagnose U0938. Each step builds on the previous one to ensure accurate diagnosis.

Step 1: Step 1: Conduct an initial visual inspection of the wiring harness and connectors associated with the trailer brake control module

Step 1: Conduct an initial visual inspection of the wiring harness and connectors associated with the trailer brake control module. Look for signs of damage, corrosion, or loose connections, which should take about 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: Use the GeekOBD APP to perform an OBD2 scan

Step 2: Use the GeekOBD APP to perform an OBD2 scan. Retrieve all diagnostic codes and freeze frame data to understand the context of the fault, which will take approximately 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: Test the suspected components using a multimeter or specialized diagnostic tools to check for continuity and functionality, which can take 20-30 minutes

Step 3: Test the suspected components using a multimeter or specialized diagnostic tools to check for continuity and functionality, which can take 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: After repairs, conduct a system function test to verify proper operation of the trailer brake system and clear any stored codes, taking about 10-15 minutes

Step 4: After repairs, conduct a system function test to verify proper operation of the trailer brake system and clear any stored codes, taking about 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: Finally, perform a road test under various conditions to ensure that the repair was successful and that the vehicle operates correctly, which will take around 15-20 minutes

Step 5: Finally, perform a road test under various conditions to ensure that the repair was successful and that the vehicle operates correctly, which will take around 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: Trailer Brake Control Module Replacement in 2016 Chevy Silverado

Vehicle: 2016 Chevrolet Silverado 1500, 75,000 miles

Problem: Customer reported intermittent trailer braking issues and the check engine light was on.

Diagnosis: After scanning with the GeekOBD APP, U0938 was confirmed along with other codes indicating a faulty brake control module.

Solution: Replaced the trailer brake control module and repaired the wiring harness.

Cost: $450 (Parts: $300 + Labor: $150)

Result: Post-repair, the customer reported consistent braking performance while towing and no further issues.

Case Study 2: Wiring Harness Repair for 2017 GMC Sierra

Vehicle: 2017 GMC Sierra 1500, 50,000 miles

Problem: The check engine light was illuminated, and the customer experienced trailer braking failures.

Diagnosis: An inspection revealed corroded connectors in the wiring harness leading to the trailer brake control module.

Solution: Cleaned and repaired the connectors, ensuring secure connections.

Cost: $150 (Parts: $50 + Labor: $100)

Result: The repair resolved the U0938 code, and the customer reported improved braking performance.

Diagnose U0938

Use GeekOBD APP for professional diagnosis!

  • Real-time data monitoring
  • Advanced diagnostic features
  • Step-by-step repair guidance
  • Professional-grade analysis
Download GeekOBD APP Get MOBD Adapter

Code Information

Code: U0938
System: Network (Communication, CAN Bus)
Severity: HIGH
Category: Network Codes