Safety Warning
- Vehicle may experience sudden loss of power or unexpected shifting
- Transmission may go into limp mode causing reduced performance
- Avoid aggressive driving or towing until diagnosed
- Do not ignore this code as it may lead to complete transmission failure
Quick Diagnosis Summary
The P0700 diagnostic trouble code in your 2020 Subaru Impreza indicates a transmission control system malfunction that requires immediate attention. This generic code signals that your vehicle's Powertrain Control Module (PCM) has detected an issue with the transmission control system, though it doesn't specify the exact problem. For Subaru Impreza owners, this code often points to serious CVT (Continuously Variable Transmission) issues that are unfortunately common in this model year.
Understanding P0700 Code in Subaru Impreza
The P0700 code serves as a gateway code that tells you there's a problem somewhere in the transmission system. When this code appears, it means your vehicle's computer has detected irregularities in transmission operation and has likely stored additional, more specific codes that will help pinpoint the exact issue. The 2020 Subaru Impreza's CVT transmission is particularly susceptible to this code due to known reliability issues with Subaru's CVT design.
Symptoms of P0700 Transmission Control System Malfunction
When your 2020 Subaru Impreza triggers the P0700 code, you'll likely notice several warning signs that indicate transmission problems:
- Check Engine Light: The most obvious symptom is the illuminated check engine light on your dashboard
- Transmission Limp Mode: Your vehicle may enter a protective "limp mode," limiting power and speed to prevent further damage
- Erratic Shifting: The CVT may exhibit unusual behavior, such as sudden RPM changes, hesitation, or jerky acceleration
- Loss of Power: You might experience reduced acceleration or difficulty maintaining highway speeds
- Strange Noises: Whining, grinding, or unusual sounds coming from the transmission area
- Transmission Overheating: The transmission temperature warning light may appear
- Complete Loss of Drive: In severe cases, the vehicle may not move forward or backward
Common Causes of P0700 in 2020 Subaru Impreza
Transmission Control Module (TCM) Failure
The most likely culprit behind P0700 in your 2020 Subaru Impreza is a failing Transmission Control Module. The TCM is the computer that manages your CVT transmission's operation. Internal faults, corrupted software, or electrical issues within the TCM can trigger this code. This problem is particularly common in Subaru CVT transmissions as they accumulate mileage, with many owners reporting TCM failures between 80,000 and 120,000 miles.
CVT Transmission Internal Failure
Subaru's CVT transmissions have a documented history of premature failure, and your 2020 Impreza is unfortunately susceptible to these issues. Internal components such as the drive belt, pulleys, or valve body can wear prematurely, leading to transmission malfunction. This typically occurs between 60,000 and 100,000 miles, though some owners have experienced issues as early as 40,000 miles.
Transmission Wiring Harness Damage
The complex wiring system connecting your transmission to the vehicle's computer can become damaged over time. Corrosion from road salt, moisture intrusion, or physical damage from road debris can disrupt communication between the TCM and transmission sensors. This is especially common in regions with harsh winter conditions where road salt is frequently used.
Low or Contaminated CVT Fluid
Your 2020 Subaru Impreza's CVT requires specific fluid (Subaru High Torque CVT Fluid) to operate properly. If the fluid level is low due to leaks or if the fluid has become contaminated or degraded, it can cause the transmission to malfunction. Subaru recommends CVT fluid changes every 60,000 miles, though many mechanics suggest more frequent intervals for better reliability.
Transmission Speed Sensor Failure
Input and output speed sensors monitor the transmission's operation and send data to the TCM. When these sensors fail, they can cause the TCM to misinterpret transmission performance and trigger the P0700 code. While less common than other causes, sensor failures do occur and can create intermittent problems that are difficult to diagnose.
Professional Diagnosis Process
Diagnosing P0700 in your 2020 Subaru Impreza requires professional equipment and expertise. The diagnostic process typically involves:
- OBD-II Scan: Reading all stored codes, including pending and manufacturer-specific codes
- TCM Communication Test: Verifying the TCM can communicate with the vehicle's main computer
- CVT Fluid Analysis: Checking fluid level, color, and condition for signs of internal damage
- Electrical Testing: Examining wiring harnesses and connections for damage or corrosion
- Transmission Performance Test: Road testing to observe transmission behavior under various conditions
- Sensor Verification: Testing individual sensors for proper operation and signal quality
Repair Options and Costs
Repairing P0700 issues in your 2020 Subaru Impreza is strictly a professional-only job due to the complexity of modern CVT systems. Here's what you can expect:
Professional Repair Costs
- TCM Replacement: $800-$1,200 including programming
- CVT Fluid Service: $200-$400 for complete fluid exchange
- Wiring Repair: $300-$800 depending on extent of damage
- Sensor Replacement: $200-$500 per sensor
- CVT Transmission Replacement: $4,000-$6,000 (if internal failure is confirmed)
Warranty Considerations
If your 2020 Subaru Impreza is still under warranty, CVT transmission issues may be covered. Subaru has extended CVT warranties for many models due to known reliability problems. Check with your Subaru dealer about potential warranty coverage before paying for repairs out of pocket.
Prevention and Maintenance Tips
While some CVT issues in the 2020 Subaru Impreza are unfortunately inevitable due to design limitations, you can take steps to maximize your transmission's lifespan:
- Regular CVT Fluid Changes: Change CVT fluid every 30,000-40,000 miles instead of Subaru's 60,000-mile recommendation
- Gentle Driving Habits: Avoid aggressive acceleration, hard braking, and frequent stop-and-go driving when possible
- Proper Warm-Up: Allow the transmission to warm up before demanding full performance, especially in cold weather
- Regular Inspections: Have your transmission inspected annually for leaks, unusual noises, or performance changes
- Address Issues Promptly: Don't ignore early warning signs like check engine lights or unusual transmission behavior
- Use Correct Fluid: Only use Subaru-approved CVT fluid; generic fluids can cause damage
Safety Warnings and Immediate Actions
If your 2020 Subaru Impreza displays the P0700 code, take these safety precautions immediately:
- Schedule professional diagnosis as soon as possible
- Avoid aggressive driving, towing, or hauling heavy loads
- Be prepared for sudden loss of power or unexpected transmission behavior
- Don't ignore the problem, as continued driving may lead to complete transmission failure
- Consider alternative transportation if symptoms are severe
Frequently Asked Questions
You should limit driving and seek professional diagnosis immediately. While the vehicle may still operate, the P0700 code indicates a transmission control system malfunction that could lead to sudden loss of power or complete transmission failure. Avoid aggressive driving, towing, or long trips until the issue is properly diagnosed and repaired.
Repair costs typically range from $800 to $1,500, depending on the underlying cause. Simple fixes like CVT fluid service may cost $200-$400, while TCM replacement can run $800-$1,200. However, if the CVT transmission itself has failed internally, replacement costs can exceed $4,000-$6,000.
CVT transmission issues may be covered under your vehicle's powertrain warranty or extended CVT warranty. Subaru has acknowledged CVT reliability problems and has extended warranties for many models. Contact your Subaru dealer to verify your specific warranty coverage before paying for repairs out of pocket.
The most common causes in 2020 Subaru Impreza include TCM (Transmission Control Module) failure, CVT internal component failure, contaminated or low CVT fluid, damaged wiring harnesses, and faulty transmission sensors. Subaru CVT transmissions are particularly prone to premature failure between 60,000-100,000 miles.
While you can clear the code using an OBD-II scanner, this won't fix the underlying problem. The P0700 code will return if the transmission control system malfunction persists. Professional diagnosis is essential to identify and repair the root cause of the problem.
Prevent CVT issues by changing the transmission fluid every 30,000-40,000 miles (more frequently than Subaru's recommendation), using only approved Subaru CVT fluid, avoiding aggressive driving habits, allowing proper warm-up time, and addressing any transmission symptoms immediately. Regular maintenance and gentle driving can help extend CVT lifespan.