U0CAC - Understanding DTC U0CAC: Common Issues in 2017-2020 Chevrolet Silverado and GMC Sierra

Quick Answer

U0CAC means: U0CAC indicates a communication error between the vehicle's engine control module and an auxiliary module.

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

Can I drive with U0CAC? Immediate diagnosis is recommended to avoid further issues.

Common Questions

What does U0CAC mean and how does it affect my car?

The U0CAC code indicates a communication issue within your vehicle's electronic systems, particularly between the engine control module and an auxiliary module. This can affect various functions of your vehicle, leading to warning lights, erratic behavior of electronic components, and potential impacts on fuel efficiency.

What are the most common causes of U0CAC and how much does it cost to fix?

Common causes of U0CAC include damaged wiring (60% likelihood), faulty auxiliary modules (30%), and software bugs (10%). Repair costs can range from $100 for wiring repairs to $800 for module replacements, depending on the severity of the issue.

Can I drive my car with U0CAC or should I stop immediately?

While it may be possible to drive your vehicle with the U0CAC code, it's not advisable. Ignoring the code can lead to further electrical issues or impact safety features. It's best to diagnose and address the problem promptly to ensure your vehicle’s reliability.

How can I diagnose U0CAC myself using GeekOBD APP?

To diagnose U0CAC with the GeekOBD APP, first connect the app to your vehicle's OBD2 port. Perform a scan to retrieve error codes and review the freeze frame data for context. Follow the on-screen instructions for component testing and system checks.

What vehicles are most commonly affected by U0CAC?

The U0CAC code is frequently reported in models like the 2017-2020 Chevrolet Silverado and GMC Sierra. These vehicles may experience issues related to the auxiliary control module that triggers this code.

How can I prevent U0CAC from happening again?

Preventive measures include regular maintenance checks of electrical connections, avoiding exposure to harsh conditions that may damage wiring, and ensuring software updates are performed as recommended by your vehicle manufacturer.

What is U0CAC?

The diagnostic trouble code (DTC) U0CAC indicates a communication issue within the vehicle's network, specifically related to the auxiliary control module. This code is common in models such as the 2017-2020 Chevrolet Silverado and GMC Sierra. When a U0CAC code is triggered, it typically signifies that the engine control module (ECM) has lost communication with one of the auxiliary modules, which can lead to various performance issues. This may manifest as warning lights on the dashboard, such as the check engine light, and can affect vehicle systems that rely on data from the affected module. In practice, this means that drivers may experience symptoms like erratic vehicle behavior, issues with electronic features (like power windows or climate control), and in some cases, a reduction in fuel efficiency. Ignoring this code can lead to further complications or even safety issues, particularly if critical systems are affected. It’s essential for owners to address this error promptly to ensure optimal functioning of their vehicle.

System: U - Network (Communication, CAN Bus)

Symptoms

Common symptoms when U0CAC is present:

  • Check engine light illuminates or flashes, indicating that there is an issue with the vehicle's electronic systems.
  • Erratic behavior of electronic components like power windows or radio, which may not respond as expected.
  • Decreased fuel economy, possibly by 10-15%, due to inefficient operation of engine management systems.
  • Delayed response from throttle or unusual shifting in automatic transmission, which may affect drivability.
  • Unusual noises from the engine area, potentially linked to malfunctioning components.

Possible Causes

Most common causes of U0CAC (ordered by frequency):

  1. The most common cause of U0CAC (about 60% likelihood) is damaged wiring or poor connections between the ECM and auxiliary module, which can occur due to wear and tear or environmental factors.
  2. Another prevalent cause (30%) is a faulty auxiliary control module itself, which may fail due to internal malfunctions or software issues.
  3. A third cause may involve software bugs in the ECM or associated modules, which can often be resolved with a simple software update.
  4. Less common but serious causes include physical damage to the control module from impacts or water intrusion, which could lead to expensive repairs.
  5. Rarely, this code may be triggered by issues within the vehicle’s CAN bus system, which requires specialized diagnostic tools to identify.

U0CAC Repair Costs

Cost Breakdown by Repair Type

Wiring Repair

Repair or replacement of damaged wiring or connectors between the ECM and auxiliary module.

  • Total: $100 - $300
  • Success rate: 80%
Auxiliary Module Replacement

Replacement of the faulty auxiliary control module identified during diagnostics.

  • Total: $300 - $800
  • Success rate: 90%
Software Update

Update the vehicle's ECM or auxiliary module to fix software-related issues.

  • Total: $50 - $150
  • Success rate: 70%
Money-Saving Tips for U0CAC
  • 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 U0CAC Diagnosis Process

Follow these systematic steps to accurately diagnose U0CAC. Each step builds on the previous one to ensure accurate diagnosis.

Step 1: Step 1: Perform an initial visual inspection to look for obvious issues like damaged wiring, loose connectors, or corrosion around the ECM and auxiliary modules (5-10 minutes)

Step 1: Perform an initial visual inspection to look for obvious issues like damaged wiring, loose connectors, or corrosion around the ECM and auxiliary modules (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 and retrieve all codes along with freeze frame data to understand the context of the fault (10-15 minutes)

Step 2: Use the GeekOBD APP to perform an OBD2 scan and retrieve all codes along with freeze frame data to understand the context of the fault (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: Conduct component testing using a multimeter to check voltage and ground signals at the affected modules (20-30 minutes)

Step 3: Conduct component testing using a multimeter to check voltage and ground signals at the affected modules (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: Run a system function test to verify that all systems are operational after making any repairs, and clear the codes to see if they return (10-15 minutes)

Step 4: Run a system function test to verify that all systems are operational after making any repairs, and clear the codes to see if they return (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: A road test should be conducted under various driving conditions to confirm that the vehicle operates without issues and that the code does not reappear (15-20 minutes)

Step 5: A road test should be conducted under various driving conditions to confirm that the vehicle operates without issues and that the code does not reappear (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: 2018 Chevy Silverado - Communication Failure

Vehicle: 2018 Chevrolet Silverado, 45,000 miles

Problem: Customer reported the check engine light was on, and various electronic features were malfunctioning.

Diagnosis: Performing a thorough diagnostic scan revealed the U0CAC code. Visual inspection showed damaged wiring near the ECM.

Solution: Repaired the damaged wiring and cleared the codes. Followed up with a system function test to ensure all electronic features were functioning correctly.

Cost: $250 (including parts and labor for wiring repair)

Result: The check engine light remained off, and all electronic features operated normally after the repair.

Case Study 2: 2020 GMC Sierra - Faulty Auxiliary Module

Vehicle: 2020 GMC Sierra, 30,000 miles

Problem: Driver experienced intermittent power issues with windows and dashboard lights; check engine light was illuminated.

Diagnosis: Diagnostics showed a U0CAC code along with other auxiliary module codes. Testing confirmed the auxiliary control module was faulty.

Solution: Replaced the auxiliary control module and updated the ECM software for compatibility.

Cost: $600 (including parts and labor for module replacement)

Result: Post-repair, the vehicle's systems functioned correctly, and no further codes were present.

Diagnose U0CAC

Use GeekOBD APP for professional diagnosis!

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Code Information

Code: U0CAC
System: Network (Communication, CAN Bus)
Severity: HIGH
Category: Network Codes