U0377 - Communication Error in Engine Control Module (ECM) for 2013-2018 Ford Fusion and Other Models

Quick Answer

U0377 means: U0377 indicates a communication error between your vehicle's ECM and other modules.

Fix: Check and replace faulty components Cost: $150 - $300 Time: 90-180 minutes

Can I drive with U0377? Immediate attention is recommended to prevent further damage.

Common Questions

What does U0377 mean and how does it affect my car?

The U0377 code indicates a communication error between your vehicle's ECM and other modules. This can lead to various performance issues, including engine hesitation and erratic transmission behavior. If left unaddressed, it may compromise the vehicle's safety and overall functionality.

What are the most common causes of U0377 and how much does it cost to fix?

Common causes include faulty wiring, a malfunctioning ECM, or software issues. Repair costs can vary significantly; wiring repairs might cost between $150-$300, whereas module replacements can range from $500-$1200 depending on the specific components involved.

Can I drive my car with U0377 or should I stop immediately?

It's advisable to stop driving your vehicle if you see the U0377 code. Continuing to drive could lead to further damage and safety issues, especially if the engine's performance is affected.

How can I diagnose U0377 myself using GeekOBD APP?

You can use the GeekOBD APP to scan your vehicle for diagnostic trouble codes. It allows you to view live data, which can help you pinpoint issues, check for freeze frame data, and monitor the vehicle's performance, aiding in your diagnosis of the U0377 code.

What vehicles are most commonly affected by U0377?

The U0377 code is commonly found in vehicles like the 2013-2018 Ford Fusion, 2014-2016 Ford Escape, and other Ford models equipped with similar ECM and TCM setups. Review any manufacturer recalls or technical service bulletins for additional insights.

How can I prevent U0377 from happening again?

Regular maintenance, including checking and securing wiring connections and keeping your vehicle's software up to date, can help prevent the U0377 code from reappearing. Ensure routine inspections of electrical components to catch potential issues early.

What is U0377?

The U0377 diagnostic trouble code (DTC) indicates that there’s an issue with communication between the Engine Control Module (ECM) and another module in your vehicle, such as the Transmission Control Module (TCM) or Body Control Module (BCM). This code often signifies that the ECM is receiving invalid data from another component, leading to potential performance issues and diagnostic complications. For example, in the case of a 2015 Ford Fusion, drivers may notice erratic engine behavior or unusual shifts in transmission performance due to this miscommunication. When the U0377 code appears, it’s essential to understand that the vehicle’s performance and safety could be compromised. Symptoms may range from a check engine light to more severe operational issues like stalling or poor acceleration. Addressing this code usually requires thorough diagnostics to pinpoint the specific fault, whether it’s a faulty module, wiring issues, or even software glitches that need updating. Ignoring this code could lead to further complications, including more extensive repairs down the line, making it crucial to take it seriously and seek professional assistance.

System: U - Network (Communication, CAN Bus)

Symptoms

Common symptoms when U0377 is present:

  • Check engine light stays on constantly, indicating a persistent issue that requires diagnostics.
  • Engine hesitates during acceleration, causing a noticeable lag when you press the gas pedal.
  • Fuel economy decreased by 10-15%, leading to more frequent trips to the gas station.
  • Transmission shifts become erratic, resulting in harsh or delayed gear changes.
  • Unusual electrical issues, such as dashboard lights flickering or intermittent function of power accessories.

Possible Causes

Most common causes of U0377 (ordered by frequency):

  1. The most common cause is faulty wiring or connectors between the ECM and other modules, occurring in about 50% of cases. Over time, wires can corrode or become loose, leading to poor communication.
  2. A malfunctioning ECM or TCM can also trigger this code, particularly if the module has suffered water damage or internal failure. This is seen in about 30% of cases.
  3. Software issues can also lead to U0377; outdated firmware may not support current vehicle functions. Keeping software updated can prevent this problem.
  4. Less common but serious causes include a failed BCM, which can affect multiple systems in the vehicle. This occurs in about 10% of cases.
  5. Rarely, external interference from aftermarket electronics can cause communication disruptions, affecting about 5% of vehicles with modifications.

U0377 Repair Costs

Cost Breakdown by Repair Type

Wiring Repair

Repairing or replacing damaged wiring or connectors between modules.

  • Total: $150 - $300
  • Success rate: 85%
Module Replacement

Replacing a faulty ECM or TCM if they are determined to be non-functional.

  • Total: $500 - $1200
  • Success rate: 90%
Software Update

Updating the ECM software to fix communication issues.

  • Total: $100 - $200
  • Success rate: 75%
Money-Saving Tips for U0377
  • 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 U0377 Diagnosis Process

Follow these systematic steps to accurately diagnose U0377. 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 around the ECM and connectors (5-10 minutes)

Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion around the ECM and connectors (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, helping you diagnose the issue more effectively (10-15 minutes)

Step 2: OBD2 scan with GeekOBD APP - Retrieve all codes and freeze frame data to understand the fault context, helping you diagnose the issue more effectively (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, verifying their functionality (20-30 minutes)

Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components, verifying their functionality (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 are made and clear codes to ensure the issue is resolved (10-15 minutes)

Step 4: System function test - Verify proper operation after repairs are made and clear codes to ensure 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 returning symptoms (15-20 minutes)

Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success and monitor for any returning symptoms (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 Fusion U0377 Code Resolution

Vehicle: 2015 Ford Fusion, 60,000 miles

Problem: Customer reported check engine light and engine hesitation.

Diagnosis: Initial scan revealed U0377 code. Wiring inspection showed corroded connectors.

Solution: Replaced corroded connectors and performed a software update on the ECM.

Cost: $250 (parts and labor)

Result: Vehicle performance improved, and check engine light remained off after the repair.

Case Study 2: 2017 Ford Escape Transmission Issues

Vehicle: 2017 Ford Escape, 45,000 miles

Problem: Driver experienced erratic transmission shifts and a persistent check engine light.

Diagnosis: Found U0377 code during diagnostics, indicating communication failure between ECM and TCM.

Solution: Replaced the TCM after confirming it was malfunctioning.

Cost: $800 (including parts and labor)

Result: Smooth transmission operation restored; no further issues reported after repair.

Diagnose U0377

Use GeekOBD APP for professional diagnosis!

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  • Professional-grade analysis
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Code Information

Code: U0377
System: Network (Communication, CAN Bus)
Severity: HIGH
Category: Network Codes