U0077 - Understanding Communication Bus A Off: Common Issues in 2015-2020 Ford F-150 and More

Quick Answer

U0077 means: DTC U0077 indicates a communication failure in the vehicle's CAN bus A system.

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

Can I drive with U0077? Immediate attention is recommended to avoid further complications.

Common Questions

What does U0077 mean and how does it affect my car?

DTC U0077 indicates a communication failure between the vehicle's control modules. This can lead to erratic engine behavior, issues with electronic components, and can severely impact your vehicle's performance and safety if left unresolved.

What are the most common causes of U0077 and how much does it cost to fix?

Common causes include faulty wiring (50% likelihood), defective control modules (30%), and poor connections due to corrosion (15%). Repair costs can range from $100 for wiring issues to over $1,200 for control module replacements, depending on the specific problem.

Can I drive my car with U0077 or should I stop immediately?

While you may still be able to drive, it is not advisable to ignore U0077. Continuing to drive with this code can lead to further issues, including complete loss of vehicle control or safety features. It's best to have it diagnosed as soon as possible.

How can I diagnose U0077 myself using GeekOBD APP?

Using the GeekOBD APP, connect to your vehicle's OBD2 port, retrieve the DTCs, and access freeze frame data. This will help you understand when the error occurred and under what conditions, which is crucial for diagnosing the issue accurately.

What vehicles are most commonly affected by U0077?

DTC U0077 is commonly found in vehicles like the 2015-2020 Ford F-150, 2016-2019 Chevrolet Silverado, and various models from Dodge and Toyota. Check for any recalls or Technical Service Bulletins (TSBs) related to your specific vehicle.

How can I prevent U0077 from happening again?

Regular maintenance checks, including inspecting the wiring and connectors for wear, ensuring your battery is in good condition, and updating your vehicle's software, can help prevent U0077 from recurring.

What is U0077?

DTC U0077 refers to a communication error within the vehicle's network, specifically indicating that the Control Area Network (CAN) bus A is not functioning correctly. The CAN bus is essential for allowing various modules in your vehicle to communicate effectively, including the engine control module (ECM), transmission control module (TCM), and body control module (BCM). When the U0077 code is triggered, it suggests that one or more of these modules are unable to send or receive messages, which can result in a multitude of performance issues. For instance, you may experience erratic behavior from electronic components, such as inconsistent power steering, malfunctioning dashboard indicators, or even stalling. The implications of this code can be significant, leading to decreased vehicle reliability and safety. It's vital to address U0077 promptly, as ignoring the issue could result in further damage and costly repairs down the line. Common vehicles affected by this code include the 2015-2020 Ford F-150, 2016-2019 Chevrolet Silverado, and various models from brands like Dodge and Toyota. If you're experiencing symptoms related to this code, it's advisable to consult a professional technician for a thorough diagnosis and repair.

System: U - Network (Communication, CAN Bus)

Symptoms

Common symptoms when U0077 is present:

  • Check engine light remains illuminated, indicating an underlying issue that requires attention.
  • Electrical systems acting erratically, such as power windows or door locks failing to operate as expected.
  • Loss of power steering assist, making the vehicle difficult to maneuver, especially at low speeds.
  • Erratic dashboard readings, including fluctuating RPM and speedometer readings, leading to driver confusion.
  • Inconsistent engine performance, including stalling or hesitation during acceleration due to lack of communication between modules.

Possible Causes

Most common causes of U0077 (ordered by frequency):

  1. Faulty wiring or connectors in the CAN bus system - A common cause with about 50% likelihood, often due to wear and tear or damage.
  2. Defective control modules - This includes ECM, BCM, or TCM, which can fail to communicate due to internal faults, occurring in roughly 30% of cases.
  3. Corrosion or poor connections at terminals - Regular exposure to moisture can lead to corrosion, affecting 15% of cases and prevent effective data transmission.
  4. Less common cause includes software issues or firmware glitches in the control modules, which can occur in newer vehicles.
  5. Rarely, issues like a failing battery or alternator can lead to voltage drops affecting CAN bus communication.

U0077 Repair Costs

Cost Breakdown by Repair Type

Wiring Repair/Replacement

Repairing or replacing damaged wiring or connectors in the CAN bus system.

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

Replacing faulty control modules such as ECM or BCM.

  • Total: $400 - $1200
  • Success rate: 90%
Money-Saving Tips for U0077
  • 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 U0077 Diagnosis Process

Follow these systematic steps to accurately diagnose U0077. Each step builds on the previous one to ensure accurate diagnosis.

Step 1: Step 1: Initial visual inspection - Check for damaged wiring, loose connections, or corrosion on the CAN bus harness (5-10 minutes)

Step 1: Initial visual inspection - Check for damaged wiring, loose connections, or corrosion on the CAN bus harness (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 - Use the app to retrieve all trouble codes and freeze frame data to understand the fault context (10-15 minutes)

Step 2: OBD2 scan with GeekOBD APP - Use the app to retrieve all trouble 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 - Utilize a multimeter to test suspected components and verify voltage levels on the CAN bus (20-30 minutes)

Step 3: Component testing - Utilize a multimeter to test suspected components and verify voltage levels on the CAN bus (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 - After making repairs, verify the operation of all related systems and clear codes to see if they return (10-15 minutes)

Step 4: System function test - After making repairs, verify the operation of all related systems and clear 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: Road test verification - Drive the vehicle under various conditions to confirm that the issue has been resolved and no new codes appear (15-20 minutes)

Step 5: Road test verification - Drive the vehicle under various conditions to confirm that the issue has been resolved and no new 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: 2017 Ford F-150 U0077 Diagnosis and Repair

Vehicle: 2017 Ford F-150, 45,000 miles

Problem: Customer reported intermittent power steering loss and check engine light.

Diagnosis: After scanning with GeekOBD APP, U0077 was confirmed. A visual inspection revealed damaged wiring in the steering control module harness.

Solution: Replaced the damaged wiring and connectors, and cleared the DTCs.

Cost: $250 (including parts and labor)

Result: The power steering function returned to normal, and no further codes appeared after a road test.

Case Study 2: 2018 Chevrolet Silverado U0077 Fix

Vehicle: 2018 Chevrolet Silverado, 30,000 miles

Problem: Customer experienced dashboard warning lights and erratic engine performance.

Diagnosis: Using GeekOBD APP, the technician found U0077 alongside other codes. The BCM was found to be defective.

Solution: Replaced the body control module and reprogrammed it to the vehicle.

Cost: $750 (parts and labor included)

Result: All systems returned to normal functionality, and the customer reported no further issues.

Diagnose U0077

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: U0077
System: Network (Communication, CAN Bus)
Severity: HIGH
Category: Network Codes