U0684 - Communication Error in CAN Bus (Common in 2014-2020 Ford Models)

Quick Answer

U0684 means: U0684 signifies a communication error in the vehicle's CAN bus system, indicating that modules are not communicating correctly.

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

Can I drive with U0684? Immediate attention is required to prevent further issues and ensure vehicle safety.

Common Questions

What does U0684 mean and how does it affect my car?

The U0684 code indicates a communication issue within your vehicle's CAN bus system. This can lead to problems with essential vehicle functions, such as engine performance and safety systems. If ignored, it may result in more severe issues and unsafe driving conditions.

What are the most common causes of U0684 and how much does it cost to fix?

Common causes include damaged wiring (60% likelihood), malfunctioning ECUs, and improper installation of aftermarket parts. Repair costs can range from $100 for wiring repairs to $1200 for ECU replacements, depending on the issue.

Can I drive my car with U0684 or should I stop immediately?

It's recommended to stop driving immediately if you see the U0684 code. The communication failure can lead to critical system failures, compromising safety and performance.

How can I diagnose U0684 myself using GeekOBD APP?

To diagnose U0684 using the GeekOBD APP, simply connect the app to your vehicle's OBD2 port. Scan for codes, and review the freeze frame data to gain insights into when the error occurred, which will help pinpoint the issue.

What vehicles are most commonly affected by U0684?

Vehicles that frequently experience the U0684 code include various Ford models such as the 2015-2018 Ford F-150 and 2016-2019 Ford Explorer. Check for any recalls or technical service bulletins (TSBs) related to your specific model.

How can I prevent U0684 from happening again?

To prevent the U0684 code from recurring, regularly inspect your vehicle's wiring and connectors for wear and corrosion, ensure proper installation of aftermarket devices, and maintain the battery and alternator in good condition.

What is U0684?

DTC U0684 indicates a communication error within the Controller Area Network (CAN) bus system of your vehicle. The CAN bus is a vital network that allows various electronic control units (ECUs) to communicate with each other. When this code appears, it means that there's a disruption in the communication between the modules, leading to potential malfunctions in essential systems like the engine, transmission, or even safety features. This disruption can manifest as erratic behavior in vehicle performance, from unresponsive controls to failure of safety systems. The implications of ignoring this code can be severe, as it may lead to a complete system failure or even unsafe driving conditions. Common models affected include the 2015-2018 Ford F-150 and 2016-2019 Ford Explorer. If you see this code, it’s crucial to address it promptly to avoid further complications and ensure your vehicle operates safely.

System: U - Network (Communication, CAN Bus)

Symptoms

Common symptoms when U0684 is present:

  • Check engine light illuminates and stays on, indicating an issue that needs immediate attention.
  • Erratic behavior in dashboard lights or gauges, leading to confusion about vehicle status.
  • Loss of functionality in key systems such as the anti-lock brake system (ABS) or stability control, which may compromise safety.
  • Engine performance issues such as stalling, poor acceleration, or hesitation during driving.
  • Inconsistent operation of electronic features like power windows or door locks, indicating broader electrical problems.

Possible Causes

Most common causes of U0684 (ordered by frequency):

  1. Most common cause is damaged wiring or connectors within the CAN bus, with a likelihood of about 60%. Regular wear and tear or corrosion can lead to these issues.
  2. A second common cause is a malfunctioning ECU, which can disrupt the communication between modules. This can arise from software glitches or physical damage.
  3. Thirdly, improper installation of aftermarket parts can interfere with the CAN bus operation; ensuring quality components and professional installation can help prevent this.
  4. A less common but serious cause is a failing battery or alternator, which can lead to voltage fluctuations affecting the entire electrical system.
  5. A rare cause might be a factory defect in the wiring harness that can lead to intermittent communication failures, typically seen in specific production runs.

U0684 Repair Costs

Cost Breakdown by Repair Type

Wiring Repair

Repair or replace damaged wiring or connectors in the CAN bus system.

  • Total: $100 - $300
  • Success rate: 85%
ECU Replacement

Replacing a faulty ECU that is causing communication issues.

  • Total: $500 - $1200
  • Success rate: 90%
Battery/Alternator Check

Testing and, if necessary, replacing the battery or alternator to ensure proper voltage supply.

  • Total: $150 - $400
  • Success rate: 75%
Money-Saving Tips for U0684
  • 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 U0684 Diagnosis Process

Follow these systematic steps to accurately diagnose U0684. Each step builds on the previous one to ensure accurate diagnosis.

Step 1: Step 1: Perform an initial visual inspection - Look for any obvious damage to wiring, connectors, or corrosion that could indicate where the issue lies (5-10 minutes)

Step 1: Perform an initial visual inspection - Look for any obvious damage to wiring, connectors, or corrosion that could indicate where the issue lies (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 scan for all codes - Retrieve the U0684 code along with any freeze frame data to understand the context of the fault (10-15 minutes)

Step 2: Use the GeekOBD APP to scan for all codes - Retrieve the U0684 code along with any 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 - Utilize a multimeter to check for continuity in the CAN bus circuits or test individual ECUs for proper operation (20-30 minutes)

Step 3: Conduct component testing - Utilize a multimeter to check for continuity in the CAN bus circuits or test individual ECUs for proper operation (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 - After repairs, verify all modules are communicating as expected and clear the code from the system (10-15 minutes)

Step 4: Run a system function test - After repairs, verify all modules are communicating as expected and clear the code from the system (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: Perform a road test - Drive the vehicle under various conditions to confirm that the repair was successful and no additional error codes appear (15-20 minutes)

Step 5: Perform a road test - Drive the vehicle under various conditions to confirm that the repair was successful and no additional error codes appear (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: Repair Case: 2016 Ford F-150 Communication Issue

Vehicle: 2016 Ford F-150, 75,000 miles

Problem: Customer reported intermittent loss of power steering and ABS warning light.

Diagnosis: After scanning with the GeekOBD APP, the U0684 code was found. A visual inspection revealed damaged wiring in the CAN bus.

Solution: Repaired the damaged wiring and ensured all connections were secure.

Cost: $250 for parts and labor

Result: The vehicle's systems returned to normal operation, and no further issues were reported.

Case Study 2: Repair Case: 2017 Ford Explorer ECU Failure

Vehicle: 2017 Ford Explorer, 60,000 miles

Problem: Customer experienced erratic dashboard readings and engine stalling.

Diagnosis: The GeekOBD APP indicated U0684 alongside other codes pointing to ECU failure.

Solution: Replaced the faulty ECU and updated the software.

Cost: $900 for ECU replacement and programming

Result: The vehicle performed well post-repair, with no further diagnostic codes.

Diagnose U0684

Use GeekOBD APP for professional diagnosis!

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  • Step-by-step repair guidance
  • Professional-grade analysis
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Code Information

Code: U0684
System: Network (Communication, CAN Bus)
Severity: HIGH
Category: Network Codes