What causes the transmission to hesitate when shifting gears in a 2019 Toyota Corolla?

When a 2019 Toyota Corolla experiences hesitation when shifting gears, it can be attributed to several potential causes. Below is a detailed guide to diagnose and address this issue.

Symptoms

• Hesitation or delay when shifting gears
• Rough or jerky gear changes
• Check Engine Light may be illuminated
• Unusual noises during gear shifts

Diagnostic Steps

1. Check for Error Codes

   • Tool Required: OBD-II Scanner
   • Procedure: Connect the OBD-II scanner to the vehicle's diagnostic port, typically located under the dashboard. Scan for any transmission-related error codes. Common codes might include P0700 (Transmission Control System Malfunction) or P0730 (Incorrect Gear Ratio).

2. Inspect Transmission Fluid

   • Tools Required: Clean rag, Funnel, Transmission fluid dipstick
   • Procedure:
     • Ensure the vehicle is on a level surface and the engine is warm.
     • Locate the transmission fluid dipstick, remove it, and wipe it clean.
     • Reinsert the dipstick fully, then remove it again to check the fluid level and condition.
     • The fluid should be at the correct level and have a reddish color. If it appears dark or has a burnt smell, it may need replacing.

3. Check for Software Updates

   • Procedure: Contact a Toyota dealership to verify if there are any software updates or Technical Service Bulletins (TSBs) related to transmission performance. Software updates can sometimes resolve shifting issues.

4. Inspect Transmission Components

   • Tools Required: Socket set, Wrench set
   • Procedure:
     • Visually inspect the transmission for any signs of leaks or damage.
     • Check the condition of the transmission mounts for wear or damage, which can affect shifting.

5. Test the Transmission Solenoids

   • Tools Required: Multimeter
   • Procedure:
     • Disconnect the transmission solenoid connectors.
     • Use a multimeter to check the resistance of each solenoid. Compare the readings with the specifications in the service manual.
     • Faulty solenoids can cause shifting delays and may need replacement.

Parts/Components That May Need Replacement

• Transmission fluid (if contaminated or low)
• Transmission solenoids (if faulty)
• Transmission filter (if clogged)
• Transmission mounts (if damaged)

Estimated Time for Repair/Maintenance

• Transmission fluid check and top-up: 30 minutes
• Transmission fluid and filter replacement: 1-2 hours
• Solenoid testing and replacement: 2-3 hours
• Software update: 1 hour (at dealership)

Safety Warnings

• Ensure the vehicle is securely lifted and supported if you need to work underneath it.
• Be cautious of hot engine components when checking fluid levels.
• Always disconnect the battery before performing electrical tests to avoid short circuits.

By following these steps, you can effectively diagnose and address the transmission hesitation issue in a 2019 Toyota Corolla. If the problem persists after these checks, it may be necessary to consult a professional technician or visit a Toyota service center for further diagnosis.