Quick Answer
U0746 means: DTC U0746 indicates a transmission control module communication error, particularly in Chrysler and Dodge vehicles.
Can I drive with U0746? Immediate attention is recommended to prevent further transmission damage.
Common Questions
What does U0746 mean and how does it affect my car?
DTC U0746 indicates a communication issue between the transmission control module and vehicle systems, potentially leading to poor shifting, reduced power, and safety concerns.
What are the most common causes of U0746 and how much does it cost to fix?
Common causes include a faulty TCM, damaged wiring, or low transmission fluid, with repair costs ranging from $100 to $700 depending on the issue.
Can I drive my car with U0746 or should I stop immediately?
It's advisable to stop driving and address the issue immediately, as continued operation can lead to significant transmission damage.
How can I diagnose U0746 myself using GeekOBD APP?
Using the GeekOBD APP, connect to your vehicle, read the diagnostic codes, and check freeze frame data for insights into the fault, allowing you to understand the situation better.
What vehicles are most commonly affected by U0746?
Commonly affected vehicles include the 2015-2018 Dodge Charger, 2016 Chrysler 300, and other models from Chrysler and Dodge produced around this time.
How can I prevent U0746 from happening again?
Regular maintenance, including checking transmission fluid levels and ensuring proper wiring conditions, can help prevent future occurrences of this code.
What is U0746?
DTC U0746 is a diagnostic trouble code indicating a communication issue between the transmission control module (TCM) and other vehicle systems, particularly in Chrysler and Dodge vehicles, such as the 2015 Dodge Charger and 2016 Chrysler 300. This code suggests that the TCM is unable to receive or send data properly, which may lead to erratic shifting, reduced engine performance, or even transmission failure. The implications of this code can be significant, as it affects the vehicle's ability to shift gears smoothly, which can ultimately affect drivability and safety. When this code appears, the check engine light will typically illuminate, and drivers may experience issues such as harsh shifting, delayed engagement, or slipping transmission. Ignoring this code can lead to further complications, including costly repairs or complete transmission failure. It's crucial for car owners to understand that timely diagnostics and repairs can prevent further damage and enhance vehicle reliability.
System: U - Network (Communication, CAN Bus)
Symptoms
Common symptoms when U0746 is present:
- The check engine light remains illuminated, signaling a potential issue with the transmission.
- Drivers may notice harsh or erratic shifting, leading to a bumpy driving experience.
- Engine performance issues such as delayed acceleration or unexpected engine revving can occur.
- Fuel economy may decrease significantly, potentially by 10-15%, due to inefficient transmission operation.
- In some cases, the vehicle may enter 'limp mode', restricting speed and power to prevent further damage.
Possible Causes
Most common causes of U0746 (ordered by frequency):
- The most common cause of U0746 is a faulty TCM, occurring in about 40% of cases. This can result from electrical faults or internal failures.
- An issue with the wiring harness or connectors, accounting for roughly 30% of cases. Damaged wires can disrupt communication between the TCM and the engine control unit.
- Low transmission fluid levels or dirty fluid can also trigger this code, making up about 20% of the cases. Regular maintenance and checks can prevent this.
- Less common causes include software malfunctions or updates needed for the TCM, which can occur in newer models.
- A rare but serious issue could be internal transmission damage, leading to costly repairs if not addressed promptly.
U0746 Repair Costs
Cost Breakdown by Repair Type
Transmission Control Module Replacement
Replacing the faulty TCM is often necessary to resolve the U0746 code.
- Total: $400 - $700
- Success rate: 90%
Wiring Harness Repair
Repairing or replacing damaged wiring to restore communication can be a more budget-friendly option.
- Total: $100 - $300
- Success rate: 75%
Money-Saving Tips for U0746
- 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 U0746 Diagnosis Process
Follow these systematic steps to accurately diagnose U0746. 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
Step 1: Initial visual inspection - Check for obvious signs like damaged wiring, loose connections, or corrosion. This can take about 5-10 minutes.
Step 2: Step 2: OBD2 scan with GeekOBD APP - Retrieve all codes and freeze frame data to understand the fault context
Step 2: OBD2 scan with GeekOBD APP - Retrieve all codes and freeze frame data to understand the fault context. This step typically takes 10-15 minutes.
Step 3: Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components like the TCM and related wiring
Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components like the TCM and related wiring. Expect this to take 20-30 minutes.
Step 4: Step 4: System function test - After any repairs, verify proper operation and clear codes
Step 4: System function test - After any repairs, verify proper operation and clear codes. This step usually takes 10-15 minutes.
Step 5: Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success, which may take 15-20 minutes
Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success, which may take 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 in a 2016 Dodge Charger
Vehicle: 2016 Dodge Charger, 50,000 miles
Problem: Customer reported check engine light, harsh shifting.
Diagnosis: OBD2 scan revealed U0746 code. Visual inspection showed a faulty TCM.
Solution: Replaced TCM and performed system function test. Cleared codes.
Cost: $650 (parts $450, labor $200)
Result: Vehicle returned to normal operation, no further issues reported.
Case Study 2: Wiring Repair on a 2015 Chrysler 300
Vehicle: 2015 Chrysler 300, 80,000 miles
Problem: Customer noticed delayed shifts and a check engine light.
Diagnosis: Diagnostic test indicated U0746 and inspection found damaged wiring.
Solution: Repaired wiring harness and updated TCM software.
Cost: $150 (parts $50, labor $100)
Result: Shifting issues resolved, customer satisfied with repair.