Quick Answer
U0747 means: DTC U0747 indicates a communication failure between the TCM and other vehicle modules.
Can I drive with U0747? Address immediately to prevent transmission damage.
Common Questions
What does U0747 mean and how does it affect my car?
DTC U0747 signifies a communication error between the TCM and other control modules. If this occurs, your vehicle may experience erratic shifting, reduced power, or even a failure to accelerate properly. It can lead to serious transmission issues if not addressed promptly.
What are the most common causes of U0747 and how much does it cost to fix?
Common causes include damaged wiring (60% likelihood), software glitches, or a faulty TCM. Repair costs vary, with wiring repairs ranging from $150 to $500, software updates costing $100 to $200, and TCM replacement between $600 and $1,200.
Can I drive my car with U0747 or should I stop immediately?
It is advised to stop driving your vehicle if you see the U0747 code, as continuing to drive can lead to severe transmission damage and safety risks. Have the vehicle diagnosed and repaired as soon as possible.
How can I diagnose U0747 myself using GeekOBD APP?
To diagnose U0747 using the GeekOBD APP, connect the app to your vehicle's OBD2 port. Run a full scan to retrieve all diagnostic codes and review freeze frame data to understand when the issue occurs. Look for any other related codes that may provide additional context.
What vehicles are most commonly affected by U0747?
Commonly affected vehicles include the 2015-2019 Chevrolet Silverado and GMC Sierra. These models have been known to encounter this code due to their specific transmission control systems.
How can I prevent U0747 from happening again?
To prevent U0747 from recurring, perform regular maintenance on your vehicle's electrical system, including checking for wear and tear on wiring and connectors. Keeping software updated and ensuring that aftermarket modifications do not interfere with the vehicle's systems can also help.
What is U0747?
DTC U0747 is a diagnostic trouble code that indicates a communication issue between the transmission control module (TCM) and other control modules in the vehicle. When this code is triggered, it typically means that the TCM is unable to communicate correctly with the engine control module (ECM) or other modules, which can lead to various performance problems. Commonly seen in 2015-2019 Chevrolet Silverado and GMC Sierra models, this code can manifest in symptoms like erratic shifting, reduced power, or even complete transmission failure if left unaddressed. The underlying cause of U0747 can often stem from issues such as damaged wiring, faulty connectors, or even software glitches. It’s important to understand that this code doesn’t just affect how your vehicle drives; it can lead to increased wear and tear on the transmission system, which can be costly to repair. If you see this code, it’s a signal to take action quickly to diagnose and resolve the problem to prevent further damage and ensure safe driving conditions.
System: U - Network (Communication, CAN Bus)
Symptoms
Common symptoms when U0747 is present:
- Check engine light stays on constantly, indicating a persistent issue with vehicle communication.
- Engine hesitates during acceleration, which can lead to poor driving experience and safety risks.
- Fuel economy decreased by 10-15%, as the transmission may not shift optimally due to communication issues.
- Rough or erratic shifting when changing gears, making the driving feel jerky and uncomfortable.
- Increased engine RPMs without corresponding speed increase, indicating potential transmission slippage.
Possible Causes
Most common causes of U0747 (ordered by frequency):
- Most common cause: Damaged wiring or connectors (60% likelihood) that disrupts communication between the TCM and ECM. Regular inspection can help prevent this.
- Second most common cause: Software glitches or outdated firmware in the TCM, which can often be resolved by updating the software.
- Third cause: Faulty transmission control module itself, which may require replacement if diagnostics confirm its failure.
- Less common but serious cause: Internal transmission failure that could lead to complete transmission breakdown.
- Rare but possible cause: Electrical interference from aftermarket modifications that can disrupt communication signals.
U0747 Repair Costs
Cost Breakdown by Repair Type
Wiring repair or replacement
Repair or replace damaged wiring or connectors that are causing communication failures.
- Total: $150 - $500
- Success rate: 85%
TCM reprogramming
Updating the transmission control module's software to resolve communication issues.
- Total: $100 - $200
- Success rate: 70%
Transmission control module replacement
Replacing the TCM if it is determined to be faulty.
- Total: $600 - $1,200
- Success rate: 90%
Money-Saving Tips for U0747
- 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 U0747 Diagnosis Process
Follow these systematic steps to accurately diagnose U0747. 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, ensuring they function correctly (20-30 minutes)
Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components, ensuring they function correctly (20-30 minutes).
Step 4: Step 4: System function test - Verify proper operation after repairs and clear codes to ensure no reoccurrence (10-15 minutes)
Step 4: System function test - Verify proper operation after repairs and clear codes to ensure no reoccurrence (10-15 minutes).
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).
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 Communication Issue in 2017 Chevrolet Silverado
Vehicle: 2017 Chevrolet Silverado, 80,000 miles
Problem: Customer complained of erratic shifting and engine power loss.
Diagnosis: Initial scan revealed U0747 along with other related codes. A visual inspection found frayed wiring near the transmission connector.
Solution: Repaired the damaged wiring and reprogrammed the TCM.
Cost: $350 (including parts and labor)
Result: Customer reported smooth shifting and improved performance after the repair.
Case Study 2: Faulty TCM in 2016 GMC Sierra
Vehicle: 2016 GMC Sierra, 65,000 miles
Problem: Check engine light was on and vehicle experienced delayed shifting.
Diagnosis: OBD2 scan confirmed U0747. Further testing showed the TCM was not responding properly.
Solution: Replaced the TCM and updated the software.
Cost: $800 (cost breakdown: $600 for TCM, $200 for labor)
Result: Vehicle performed normally after the replacement, with no further issues reported.