Quick Answer
P0738 means: P0738 indicates a transmission range performance problem where the actual gear ratio does not match the expected ratio.
Can I drive with P0738? Immediate attention is recommended to prevent further transmission damage.
Common Questions
What does P0738 mean and how does it affect my car?
The P0738 code indicates that your vehicle's transmission is having difficulties, specifically with the gear ratios. This can lead to poor acceleration, reduced fuel efficiency, and an overall negative impact on vehicle performance. If ignored, it could result in more severe transmission damage and costly repairs.
What are the most common causes of P0738 and how much does it cost to fix?
Common causes include low transmission fluid (cost-effective fix), faulty solenoids, or a malfunctioning TCM. Repair costs can range from $100 for fluid changes to over $1,500 for TCM replacements, depending on the issue.
Can I drive my car with P0738 or should I stop immediately?
Driving with a P0738 code is not recommended. It can lead to further transmission damage. If you notice symptoms like harsh shifting or unusual noises, it’s best to stop driving and seek professional diagnosis.
How can I diagnose P0738 myself using GeekOBD APP?
Using the GeekOBD APP, you can perform an OBD2 scan to retrieve the P0738 code and any related fault codes. Review the freeze frame data to understand the conditions under which the code was triggered, and check for any other codes that may provide additional context.
What vehicles are most commonly affected by P0738?
Commonly affected vehicles include the 2015-2018 Honda Accord and the Ford Fusion. Both models have reported issues related to transmission performance, making it essential for owners to remain vigilant for symptoms of P0738.
How can I prevent P0738 from happening again?
Regular transmission fluid checks and changes, keeping an eye on your vehicle's performance, and having routine diagnostics can help prevent P0738 from recurring. Additionally, addressing any early signs of transmission issues can save you from costly repairs.
What is P0738?
The diagnostic trouble code (DTC) P0738 indicates a transmission range performance issue, specifically relating to the incorrect gear ratio detected by the vehicle's transmission control module (TCM). This can manifest when the transmission isn't shifting as expected, leading to poor vehicle performance. When your car encounters this code, it suggests that the TCM has identified that the actual gear ratio does not match the expected ratio for the current driving conditions. This may be due to various reasons, including low transmission fluid levels, a faulty transmission control module, or issues with transmission solenoids. In practical terms, if you’re experiencing this code, your vehicle may struggle to shift gears smoothly, resulting in sluggish acceleration or difficulty maintaining speed. Ignoring this code can lead to significant damage to your transmission system, potentially costing thousands in repairs. Therefore, addressing the P0738 code promptly is crucial for maintaining the health of your vehicle and ensuring safe operation.
System: P - Powertrain (Engine, Transmission, Emissions)
Symptoms
Common symptoms when P0738 is present:
- The check engine light illuminates or stays on constantly, indicating a potential transmission problem.
- You may experience engine hesitation during acceleration, making it difficult to merge into traffic or drive uphill.
- Fuel economy could decrease by 10-15%, resulting in more frequent trips to the gas station.
- Shifting becomes erratic, with noticeable delays or harshness when changing from one gear to another.
- Unusual noises, such as grinding or whining, may occur when the vehicle is in gear, indicating internal transmission issues.
Possible Causes
Most common causes of P0738 (ordered by frequency):
- The most common cause of P0738 is low transmission fluid levels, which can lead to insufficient hydraulic pressure (60% likelihood). Regular fluid checks and timely changes can prevent this issue.
- A malfunctioning transmission control module (TCM) can incorrectly interpret signals, leading to shifting problems. Ensuring software updates and TCM health checks can help mitigate this risk.
- Faulty transmission solenoids that control fluid flow can lead to incorrect gear engagement. Regular vehicle inspections can help catch these issues early.
- Less common but serious causes include internal transmission damage, which may require a complete rebuild or replacement. This is often accompanied by severe symptoms like grinding noises.
- A rare cause could be a wiring issue or short circuit that disrupts communication between the TCM and transmission, potentially leading to multiple performance-related codes.
P0738 Repair Costs
Cost Breakdown by Repair Type
Transmission Fluid Change
Replacing low or contaminated transmission fluid to restore proper hydraulic pressure.
- Total: $100 - $200
- Success rate: 75%
Replace Faulty Solenoid
Replacing one or more transmission solenoids to ensure proper gear engagement.
- Total: $300 - $600
- Success rate: 85%
TCM Replacement
Replacing the transmission control module to correct erroneous signals.
- Total: $700 - $1500
- Success rate: 90%
Money-Saving Tips for P0738
- 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 P0738 Diagnosis Process
Follow these systematic steps to accurately diagnose P0738. 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, including the TCM and solenoids (20-30 minutes)
Step 3: Component testing - Use a multimeter or specific diagnostic tools to test suspected components, including the TCM and solenoids (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 Fluid Change on 2015 Honda Accord
Vehicle: 2015 Honda Accord, 85,000 miles
Problem: Customer reported check engine light and sluggish acceleration.
Diagnosis: OBD2 scan revealed P0738 and low transmission fluid levels.
Solution: Performed a transmission fluid change and cleared the code.
Cost: $150 (fluid and labor)
Result: Customer reported improved performance and no recurrence of the code.
Case Study 2: Solenoid Replacement on 2016 Ford Fusion
Vehicle: 2016 Ford Fusion, 70,000 miles
Problem: Vehicle experienced harsh shifting and check engine light on.
Diagnosis: Diagnostic tests indicated a faulty transmission solenoid, confirmed by testing.
Solution: Replaced the faulty solenoid and performed a fluid flush.
Cost: $450 (solenoid and labor)
Result: Post-repair, the vehicle shifted smoothly with no codes present.