Quick Answer
P0799 means: P0799 indicates a transmission speed sensor range or performance issue.
Can I drive with P0799? Immediate attention is recommended to avoid further damage to the transmission.
Common Questions
What does P0799 mean and how does it affect my car?
P0799 signifies a problem with the transmission speed sensor. This can impact your car's shifting capabilities, leading to poor performance and potential damage if not addressed. You may notice sluggish acceleration or jerking during gear changes.
What are the most common causes of P0799 and how much does it cost to fix?
The most common causes include a faulty transmission speed sensor or wiring issues, with repair costs typically ranging from $200 to $400 for sensor replacement. Wiring repairs might cost between $100 and $300.
Can I drive my car with P0799 or should I stop immediately?
It's advisable to stop driving your vehicle as soon as you notice the P0799 code. Continuing to drive can worsen the problem and lead to more expensive repairs.
How can I diagnose P0799 myself using GeekOBD APP?
To diagnose P0799, connect the GeekOBD APP to your vehicle's OBD2 port. Use the app to scan for codes, review freeze frame data, and monitor the sensor's performance in real-time.
What vehicles are most commonly affected by P0799?
Vehicles commonly affected by the P0799 code include the 2008-2018 Honda Accord, Toyota Camry, and Nissan Altima. It's essential to check for any recalls or technical service bulletins related to these models.
How can I prevent P0799 from happening again?
Regular maintenance, including checking transmission fluid levels, ensuring proper wiring connections, and replacing worn sensors, can help prevent recurrence of the P0799 code.
What is P0799?
The diagnostic trouble code (DTC) P0799 indicates a range or performance issue with the transmission speed sensor. This sensor is crucial for the vehicle's transmission control module (TCM) to determine the correct gear and shift timing. When this code is triggered, it typically means that the TCM is receiving readings from the transmission speed sensor that are outside of the expected range. This can lead to erratic shifting, poor acceleration, and even increased fuel consumption. The performance of the vehicle may degrade, and the check engine light may illuminate as a warning. If left unaddressed, the issue could lead to more severe transmission problems, potentially requiring extensive repairs or even replacement of the transmission. Common vehicles affected by this code include models from Honda, Toyota, and Nissan, particularly those manufactured from 2008 to 2018. Owners should be vigilant for symptoms and seek prompt diagnostics to prevent further damage.
System: P - Powertrain (Engine, Transmission, Emissions)
Symptoms
Common symptoms when P0799 is present:
- Check engine light stays on constantly, indicating a persistent issue that needs attention.
- Engine hesitates during acceleration, making driving less responsive and potentially dangerous.
- Fuel economy decreased by 10-15%, leading to increased operational costs over time.
- Transmission may slip or fail to shift properly, causing jerking movements during gear changes.
- Unusual noises from the transmission area, which could indicate deeper mechanical issues.
Possible Causes
Most common causes of P0799 (ordered by frequency):
- Faulty transmission speed sensor (60% likelihood) - This is the most common cause of the P0799 code, often due to wear and tear or electrical failure.
- Wiring harness issues (20% likelihood) - Damaged or corroded wiring can disrupt the signal between the sensor and the TCM, leading to performance problems.
- Transmission fluid issues (10% likelihood) - Low or contaminated fluid can affect sensor performance and overall transmission function.
- TCM problems (5% likelihood) - A malfunctioning transmission control module can misinterpret sensor data, causing the P0799 code to trigger.
- Rare mechanical failures (5% likelihood) - While less common, internal transmission problems can also cause this code to appear.
P0799 Repair Costs
Cost Breakdown by Repair Type
Transmission Speed Sensor Replacement
Replacing the faulty transmission speed sensor is the most common repair for DTC P0799.
- Total: $200 - $400
- Success rate: 90%
Wiring Harness Repair
Repairing or replacing damaged wiring can resolve the transmission signal issue.
- Total: $100 - $300
- Success rate: 80%
Transmission Control Module Replacement
In rare cases, replacing the TCM may be necessary if it is found to be malfunctioning.
- Total: $500 - $1,200
- Success rate: 70%
Money-Saving Tips for P0799
- 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 P0799 Diagnosis Process
Follow these systematic steps to accurately diagnose P0799. 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 the transmission speed sensor and its wiring (20-30 minutes)
Step 3: Component testing - Use a multimeter or specific diagnostic tools to test the transmission speed sensor and its wiring (20-30 minutes).
Step 4: Step 4: System function test - Verify proper operation after repairs and clear codes using the GeekOBD APP (10-15 minutes)
Step 4: System function test - Verify proper operation after repairs and clear codes using the GeekOBD APP (10-15 minutes).
Step 5: Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success and ensure smooth operation (15-20 minutes)
Step 5: Road test verification - Drive the vehicle under various conditions to confirm repair success and ensure smooth operation (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: Speed Sensor Replacement on a 2015 Honda Accord
Vehicle: 2015 Honda Accord, 75,000 miles
Problem: Customer reported erratic shifting and check engine light.
Diagnosis: OBD2 scan revealed P0799. Visual inspection showed a faulty speed sensor.
Solution: Replaced the transmission speed sensor and cleared the codes.
Cost: $300 (sensor $200, labor $100)
Result: Shifting returned to normal, and no further issues were reported.
Case Study 2: Wiring Repair on a 2010 Toyota Camry
Vehicle: 2010 Toyota Camry, 90,000 miles
Problem: Customer experienced poor acceleration and check engine light.
Diagnosis: P0799 confirmed via scan; inspection revealed damaged wiring.
Solution: Repaired the wiring harness and checked connectivity.
Cost: $150 (labor included)
Result: Vehicle performance improved significantly; no further codes appeared.