U0085 - Communication Bus A Off - Common in 2014-2020 Ford F-150 and More

Quick Answer

U0085 means: U0085 signifies a communication failure in the vehicle's internal network, preventing modules from exchanging data.

Fix: Check and replace faulty components Cost: $150 - $500 Time: 90-180 minutes

Can I drive with U0085? Immediate attention is recommended to avoid safety issues and costly repairs.

Common Questions

What does U0085 mean and how does it affect my car?

The U0085 code indicates a communication breakdown within your vehicle's internal systems, which can lead to various performance issues. It may cause erratic behavior in critical systems such as braking and engine management, ultimately affecting safety and reliability.

What are the most common causes of U0085 and how much does it cost to fix?

Common causes include faulty wiring or connectors, malfunctioning control modules, and poor ground connections. Repair costs can range from $150 for wiring repairs to $1,500 for ECM replacement.

Can I drive my car with U0085 or should I stop immediately?

While you may be able to drive your vehicle, it is not advisable. Ignoring the U0085 code can lead to safety hazards and more significant repairs, so it's best to address the issue as soon as possible.

How can I diagnose U0085 myself using GeekOBD APP?

Use the GeekOBD APP to scan for trouble codes and view freeze frame data. This will help you understand the context of the U0085 code and guide your next steps in troubleshooting and repairs.

What vehicles are most commonly affected by U0085?

The U0085 code frequently appears in models like the 2015-2018 Honda Accord, 2014-2020 Ford F-150, and numerous General Motors vehicles, especially when they have electrical system issues.

How can I prevent U0085 from happening again?

Regular maintenance, including inspections of electrical connections and ensuring proper grounding, can help prevent U0085. Keeping your vehicle's wiring in good condition will also reduce the risk of communication failures.

What is U0085?

The diagnostic trouble code (DTC) U0085 indicates a communication issue within the vehicle's CAN (Controller Area Network) bus. Essentially, it means that the transmission of data between various control modules in the vehicle has been disrupted. This code is often triggered when the engine control module (ECM) fails to receive signals from another module, which can lead to a range of performance issues. For example, if the anti-lock braking system (ABS) module or transmission control module (TCM) is not communicating properly with the ECM, you may notice erratic braking or shifting performance. Real-world implications include potential safety hazards, as critical systems may not function as intended. Vehicle owners should be aware that ignoring this code can lead to more significant problems down the line, such as increased repair costs and reduced vehicle reliability. Common vehicles affected include the 2015-2018 Honda Accord, 2014-2020 Ford F-150, and several models from General Motors. Regular diagnostics can help identify the issue before it escalates, as electrical problems can be complex and require skilled troubleshooting.

System: U - Network (Communication, CAN Bus)

Symptoms

Common symptoms when U0085 is present:

  • Check engine light stays on constantly, indicating a persistent communication issue that may require immediate attention.
  • Erratic engine performance, such as hesitation or stalling during acceleration, which can be alarming while driving.
  • Decreased fuel economy, potentially by 10-15%, due to improper engine management caused by faulty communication.
  • Malfunctioning features like cruise control or stability control, which may become unreliable or stop working altogether.
  • Increased difficulty in starting the vehicle, where it may take multiple attempts before the engine turns over.

Possible Causes

Most common causes of U0085 (ordered by frequency):

  1. The most common cause of U0085 is a faulty wiring harness or connector, accounting for about 60% of cases. Damage from wear and tear or corrosion can disrupt communication.
  2. A malfunctioning control module, such as the ABS or TCM, can also trigger this code. If these modules are failing, they won't send or receive signals properly.
  3. Poor ground connections can lead to electrical discrepancies. Ensuring all grounds are clean and secure can help avoid this issue in the future.
  4. Less common but serious causes include a failing ECM itself, which may require replacement or reprogramming if damaged.
  5. Rarely, external factors like water intrusion or damage from accidents can lead to communication failures within the CAN bus system.

U0085 Repair Costs

Cost Breakdown by Repair Type

Wiring Harness Repair

Repair or replace damaged wiring and connectors that are affecting communication.

  • Total: $150 - $500
  • Success rate: 85%
Control Module Replacement

Replace malfunctioning control module (e.g., ABS, TCM) that is not communicating with the ECM.

  • Total: $300 - $1,200
  • Success rate: 90%
ECM Reprogramming

Reprogram or replace the ECM if it is determined to be the source of the communication failure.

  • Total: $500 - $1,500
  • Success rate: 80%
Money-Saving Tips for U0085
  • 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 U0085 Diagnosis Process

Follow these systematic steps to accurately diagnose U0085. 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 correct voltage and ground (20-30 minutes)

Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components, ensuring correct voltage and ground (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 confirm the issue is resolved (10-15 minutes)

Step 4: System function test - Verify proper operation after repairs and clear codes to confirm the issue is 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 monitor 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 monitor 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: 2015 Ford F-150 Wiring Harness Repair

Vehicle: 2015 Ford F-150, 75,000 miles

Problem: The customer reported the check engine light was on, and the vehicle experienced erratic braking performance.

Diagnosis: Using the GeekOBD APP, the technician retrieved the U0085 code and performed a visual inspection. They found corroded wiring in the harness connecting the ABS module to the ECM.

Solution: The damaged section of the wiring harness was repaired, and connections were cleaned and secured.

Cost: $250 (including labor and parts)

Result: The repair resolved the U0085 code, and the vehicle's braking performance returned to normal.

Case Study 2: 2017 Honda Accord Control Module Replacement

Vehicle: 2017 Honda Accord, 50,000 miles

Problem: Customer complained of poor acceleration and a persistent check engine light.

Diagnosis: The technician used the GeekOBD APP to confirm the U0085 code, followed by testing the TCM and ECM, which indicated a failure in the TCM.

Solution: The faulty TCM was replaced, and the system was reprogrammed to restore function.

Cost: $900 (including parts and labor)

Result: Post-repair tests showed normal operation, and the check engine light remained off.

Diagnose U0085

Use GeekOBD APP for professional diagnosis!

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  • Professional-grade analysis
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Code Information

Code: U0085
System: Network (Communication, CAN Bus)
Severity: HIGH
Category: Network Codes