Quick Answer
P0790 means: P0790 indicates a transmission speed sensor issue, affecting shifting performance.
Can I drive with P0790? Immediate diagnosis is recommended to prevent further transmission damage.
Common Questions
What does P0790 mean and how does it affect my car?
The P0790 code indicates a malfunction in the transmission speed sensor, which is responsible for providing accurate speed readings to the engine control module. This malfunction can lead to erratic shifting, reduced acceleration, and overall poor vehicle performance. If left unresolved, it may cause further damage to the transmission, leading to costly repairs.
What are the most common causes of P0790 and how much does it cost to fix?
Common causes of the P0790 code include a faulty speed sensor, damaged wiring, or low transmission fluid. Repair costs typically range from $150 for sensor replacement to $100 for wiring repairs. A full diagnosis is necessary to determine the exact cause and associated costs.
Can I drive my car with P0790 or should I stop immediately?
While you might be able to drive your vehicle with the P0790 code, it is not advisable. Continuing to drive can lead to further damage to the transmission, which can be costly to repair. It's best to get the issue diagnosed and repaired as soon as possible.
How can I diagnose P0790 myself using GeekOBD APP?
To diagnose P0790 using the GeekOBD APP, start with connecting the app to your vehicle's OBD2 port. Retrieve the error codes and check freeze frame data to understand the context of the fault. Perform visual checks and component tests as indicated in the app, and follow the suggested diagnostic steps for accurate results.
What vehicles are most commonly affected by P0790?
The P0790 code is frequently seen in models like the 2003-2008 Honda Accord and the 2007-2012 Toyota Camry. These vehicles often have reported issues with their transmission speed sensors, so owners should be vigilant.
How can I prevent P0790 from happening again?
To prevent the P0790 code from reappearing, ensure regular maintenance of your vehicle, including checking and changing transmission fluid as recommended. Inspect wiring and connectors periodically, and address any leaks or issues immediately to keep the transmission functioning optimally.
What is P0790?
The diagnostic trouble code (DTC) P0790 indicates a problem with the transmission speed sensor, which is crucial for accurate speed readings that inform the engine control module (ECM) about the vehicle's speed and gear selection. This sensor ensures that the transmission operates smoothly by providing data that helps manage shift patterns and maintain optimal engine performance. When the P0790 code is triggered, it typically means that the sensor readings are outside the expected range, suggesting a malfunction or failure of the speed sensor itself or related wiring. Car owners may notice performance issues, such as slipping gears or erratic shifting, which can lead to decreased acceleration and fuel efficiency. Ignoring this code could lead to more severe transmission issues over time, resulting in costly repairs. In many cases, vehicles affected by this issue include popular models like the 2003-2008 Honda Accord and the 2007-2012 Toyota Camry. If you see the P0790 code, it’s advisable to address it promptly to avoid further complications.
System: P - Powertrain (Engine, Transmission, Emissions)
Symptoms
Common symptoms when P0790 is present:
- Check engine light stays on constantly, indicating a persistent issue with the transmission system.
- Engine hesitates during acceleration, leading to a frustrating driving experience due to delayed responses.
- Fuel economy decreased by 10-15%, which may be noticeable at the gas pump as you fill up more frequently.
- Transmission may slip or fail to engage properly, resulting in sudden loss of power while driving.
- Harsh or erratic shifting can occur, making the driving experience uncomfortable and potentially dangerous.
Possible Causes
Most common causes of P0790 (ordered by frequency):
- The most common cause is a faulty transmission speed sensor, which accounts for approximately 60% of cases. This can be due to wear and tear or exposure to extreme conditions.
- Another likely cause is damaged wiring or connectors associated with the sensor, leading to poor signal transmission to the ECM.
- A third cause could be low transmission fluid levels or degraded fluid, which can affect sensor performance. Regular maintenance is key to preventing this.
- Less common but serious causes include internal transmission problems, such as damaged gears or clutches, which require extensive repairs.
- Rarely, an issue with the ECM itself can cause a false P0790 code, necessitating a thorough diagnostic to pinpoint.
P0790 Repair Costs
Cost Breakdown by Repair Type
Transmission Speed Sensor Replacement
Replacing the faulty transmission speed sensor with a new OEM part.
- Total: $150 - $300
- Success rate: 85%
Wiring Repair
Repairing or replacing damaged wiring and connectors for proper signal transmission.
- Total: $100 - $200
- Success rate: 75%
Transmission Fluid Change
Changing low or degraded transmission fluid to ensure smooth operation and sensor accuracy.
- Total: $80 - $150
- Success rate: 70%
Money-Saving Tips for P0790
- 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 P0790 Diagnosis Process
Follow these systematic steps to accurately diagnose P0790. 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 speed sensor and associated wiring (20-30 minutes)
Step 3: Component testing - Use a multimeter or specific diagnostic tools to test the speed sensor and associated 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 vehicle under various conditions to confirm repair success (15-20 minutes)
Step 5: Road test verification - Drive 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 Speed Sensor Replacement in 2008 Honda Accord
Vehicle: 2008 Honda Accord, 120,000 miles
Problem: Customer reported check engine light and poor acceleration.
Diagnosis: Diagnostic scan revealed P0790 code, indicating a faulty speed sensor.
Solution: Replaced the transmission speed sensor and performed a fluid change.
Cost: $250 (sensor: $150, labor: $100)
Result: Customer reported improved acceleration and no check engine light after repairs.
Case Study 2: Wiring Repair for P0790 in 2012 Toyota Camry
Vehicle: 2012 Toyota Camry, 90,000 miles
Problem: Customer experienced erratic shifting and check engine light.
Diagnosis: Found damaged wiring connected to the speed sensor.
Solution: Repaired the wiring and re-secured connections.
Cost: $150 (labor: $80, materials: $70)
Result: Shifting returned to normal, and the check engine light stayed off.