Quick Answer
U079C means: DTC U079C indicates a communication failure between the transmission control module and other modules.
Can I drive with U079C? Immediate attention is recommended to prevent transmission damage.
Common Questions
What does U079C mean and how does it affect my car?
DTC U079C signifies a communication issue between the transmission control module and other systems. This can lead to poor shifting performance, reduced fuel efficiency, and could potentially cause your vehicle to enter limp mode, which protects the engine but limits performance.
What are the most common causes of U079C and how much does it cost to fix?
Common causes include a faulty transmission control module (approx. $800 - $1200), damaged wiring (around $100 - $400), or software issues that can often be resolved with a simple update ($50 - $150).
Can I drive my car with U079C or should I stop immediately?
While you may be able to drive your vehicle for a short distance, it is not advisable to ignore this code. Continued driving can lead to more severe transmission problems and ultimately higher repair costs.
How can I diagnose U079C myself using GeekOBD APP?
Using the GeekOBD APP, you can perform a scan to retrieve the U079C code and any related codes. Pay attention to freeze frame data to see conditions when the code was set, which helps in identifying the underlying issue.
What vehicles are most commonly affected by U079C?
DTC U079C is frequently encountered in 2016-2020 Ford Focus models, but it can also appear in other vehicles from manufacturers like Honda and Chevrolet, especially those with complex transmission systems.
How can I prevent U079C from happening again?
Regular maintenance, including checking wiring and connections, keeping the software updated, and promptly addressing any signs of transmission issues can help prevent the reoccurrence of U079C.
What is U079C?
DTC U079C indicates a communication error between the vehicle's control modules, specifically concerning the transmission control module (TCM) or other related modules. This code is prevalent in various vehicle models, particularly in the 2016-2020 Ford Focus. When this code is set, the vehicle's onboard diagnostic system has detected a fault in the communication line, meaning that the TCM cannot effectively relay or receive information from other components, such as the engine control module (ECM) or the body control module (BCM). The implications of this code can be significant, leading to erratic transmission behavior, including harsh shifting, failure to shift, or even a complete inability to engage the transmission. Drivers may experience symptoms like a flashing check engine light or the vehicle going into 'limp mode' to protect the engine. Addressing this issue promptly is crucial to avoid further damage to the vehicle's transmission system, which can be costly to repair. A qualified technician should perform a thorough diagnostic to pinpoint the exact source of the communication failure, as ignoring this code could lead to more severe mechanical issues down the road.
System: U - Network (Communication, CAN Bus)
Symptoms
Common symptoms when U079C is present:
- Check engine light stays on constantly, indicating a fault in the vehicle's communication system.
- Transmission may hesitate during acceleration, causing a delay in response when pressing the gas pedal.
- Fuel economy may decrease by 10-15% due to inefficient transmission performance.
- Unexpected gear shifts, where the vehicle may shift into neutral unexpectedly.
- Loss of power during acceleration, making it difficult to maintain speed or merge into traffic.
Possible Causes
Most common causes of U079C (ordered by frequency):
- The most common cause is a faulty transmission control module, which has a 60% likelihood of being the issue. This can happen due to wear or internal failure.
- Second most common cause is damaged wiring or connectors, often resulting from corrosion or physical damage, which can disrupt communication.
- Third cause could be software issues within the TCM or ECM, which can sometimes be resolved through a software update from the manufacturer.
- Less common but serious causes include short circuits within the wiring harness, which can pose a risk of fire or complete system failure.
- A rare but possible cause is a failing body control module, which may lead to multiple issues beyond just transmission performance.
U079C Repair Costs
Cost Breakdown by Repair Type
Transmission Control Module Replacement
Replacing the faulty TCM with a new OEM part.
- Total: $800 - $1200
- Success rate: 85%
Wiring Harness Repair
Fixing or replacing damaged wiring or connectors that affect communication.
- Total: $100 - $400
- Success rate: 70%
Software Update
Updating the TCM or ECM software to resolve communication issues.
- Total: $50 - $150
- Success rate: 90%
Money-Saving Tips for U079C
- 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 U079C Diagnosis Process
Follow these systematic steps to accurately diagnose U079C. 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).
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).
Step 3: Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components (20-30 minutes)
Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components (20-30 minutes).
Step 4: Step 4: System function test - Verify proper operation after repairs and clear codes (10-15 minutes)
Step 4: System function test - Verify proper operation after repairs and clear codes (10-15 minutes).
Step 5: Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success (15-20 minutes)
Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success (15-20 minutes).
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: Transmission Control Module Replacement on a 2018 Ford Focus
Vehicle: 2018 Ford Focus, 45,000 miles
Problem: Customer reported harsh shifting and frequent engine light activation.
Diagnosis: Initial scans showed U079C alongside other transmission-related codes. Visual inspection revealed a faulty TCM.
Solution: Replaced the TCM with an OEM part and cleared the codes.
Cost: $1,000 (parts: TCM $800, labor $200)
Result: After the repair, the customer reported smooth shifting and no further warning lights.
Case Study 2: Wiring Repair on a 2017 Chevrolet Malibu
Vehicle: 2017 Chevrolet Malibu, 50,000 miles
Problem: Customer experienced intermittent transmission failure and check engine light.
Diagnosis: Diagnostic tests revealed U079C due to damaged wiring harness.
Solution: Wiring harness was repaired, and connections were restored.
Cost: $300 (parts: $100, labor $200)
Result: Post-repair, the vehicle operated normally with no codes.