What could cause the transmission to slip in a 2020 Toyota Highlander?

Toyota Highlander Fourth Generation (2020-present)

Error Codes

3-5 hours

Time

medium

Difficulty

medium

Severity

4 min read

665 words

Problem Statement

Learn about the causes of transmission slipping in the 2020 Toyota Highlander, symptoms to look for, and step-by-step diagnostic and repair instructions.

Affected Component

transmission

Estimated Time

3-5 hours

Symptoms

•Engine RPMs increase without a corresponding increase in vehicle speed.
•Delay in engagement when shifting from park to drive or reverse.
•Harsh or irregular shifting, especially under load.
•Warning lights (like the check engine light) may illuminate.
•Unusual noises (grinding, whining) during shifts.

Diagnostic Steps

1
Preliminary Check: Check for warning lights and perform a visual inspection.
2
Check Transmission Fluid Level: Inspect fluid level and add if low.
3
Inspect Transmission Fluid Condition: Check color and smell of fluid.
4
Examine the Transmission Filter: Change filter if contaminated.
5
Inspect Torque Converter Functionality: Check for shuddering and test converter.
6
Scan for Diagnostic Trouble Codes (DTCs): Retrieve and analyze any stored codes.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•transmission fluid dipstick
•flashlight
•funnel
•clean cloth
•socket set
•screwdrivers
•new transmission filter
•gasket
•torque wrench
•appropriate socket set

Related Faults

Share this solution

Comments

No comments yet

Be the first to share your thoughts

Back to Generation

Symptoms

•Engine RPMs increase without a corresponding increase in vehicle speed.

•Delay in engagement when shifting from park to drive or reverse.

•Harsh or irregular shifting, especially under load.

•Warning lights (like the check engine light) may illuminate.

•Unusual noises (grinding, whining) during shifts.

Diagnostic Steps

1
Preliminary Check: Check for warning lights and perform a visual inspection.
2
Check Transmission Fluid Level: Inspect fluid level and add if low.
3
Inspect Transmission Fluid Condition: Check color and smell of fluid.
4
Examine the Transmission Filter: Change filter if contaminated.
5
Inspect Torque Converter Functionality: Check for shuddering and test converter.
6
Scan for Diagnostic Trouble Codes (DTCs): Retrieve and analyze any stored codes.

Solution

Transmission Slipping in a 2020 Toyota Highlander

Potential Causes

Low Transmission Fluid
Contaminated Transmission Fluid
Worn Out Transmission Filter
Faulty Torque Converter
Malfunctioning Transmission Control Module (TCM)
Internal Transmission Damage (worn clutches, bands, gears)

Step 1: Preliminary Check

Tools Required: OBD-II scanner, transmission fluid dipstick (if applicable), flashlight.
Procedure:
- Start the vehicle and check for warning lights on the dashboard.
- Perform a visual inspection of the transmission area for leaks or damage.

Step 2: Check Transmission Fluid Level

Tools Required: Transmission dipstick (if applicable), funnel, clean cloth.
Procedure:
- With the engine running and the vehicle on a level surface, remove the transmission dipstick (if available).
- Wipe it clean, reinsert, and pull it out again to check the fluid level.
- If low, add the recommended type of transmission fluid according to the owner's manual.

Step 3: Inspect Transmission Fluid Condition

Tools Required: Clean cloth, transmission fluid sample jar.
Procedure:
- Inspect the fluid on the dipstick for color and smell.
- Healthy transmission fluid should be bright red and should not smell burnt. If the fluid is dark brown or has a burnt smell, it needs to be replaced.

Step 4: Examine the Transmission Filter

Tools Required: Socket set, screwdrivers, new transmission filter, gasket (if applicable).
Procedure:
- If the fluid is contaminated or the vehicle has high mileage, consider changing the transmission filter.
- Drain the fluid, remove the pan, and replace the filter. Ensure to clean the pan and replace the gasket.

Step 5: Inspect Torque Converter Functionality

Tools Required: Torque wrench, appropriate socket set.
Procedure:
- A faulty torque converter can cause slipping. Check for signs of shuddering during acceleration.
- If suspected, the torque converter should be tested for proper operation or replaced if faulty.

Step 6: Scan for Diagnostic Trouble Codes (DTCs)

Tools Required: OBD-II scanner.
Procedure:
- Connect the OBD-II scanner and retrieve any stored DTCs.
- Look for codes related to the transmission or TCM. Codes can direct you to specific issues (e.g., solenoid problems, sensor failures).

Repair Instructions

Step 1: Replenish or Replace Transmission Fluid

If fluid is low or dirty, replace it. Ensure you use the correct type of fluid (Toyota ATF WS).
Use a funnel to add fluid through the dipstick tube, and recheck the level.

Step 2: Replace Transmission Filter

Drain Transmission Fluid: Place a drain pan under the transmission, remove the drain plug, and allow fluid to drain completely.
Remove Transmission Pan: Unbolt the transmission pan and remove it. Clean the mating surfaces and remove the old gasket.
Change the Filter: Remove the old filter; install the new one according to the manufacturer’s specifications.
Reinstall Transmission Pan: Bolt the pan back on with a new gasket, ensuring it is sealed correctly to avoid leaks. Refill with fresh transmission fluid.

Step 3: Repair or Replace Torque Converter/TCM

If either the torque converter or TCM has been diagnosed as faulty, replacement will be necessary. This typically requires:
- Removing the transmission to access the torque converter.
- Disconnecting electrical connectors and fluid lines.
- Carefully reinstalling the new components, ensuring proper alignment and connection.

Conclusion

If after following these steps the transmission still slips, it may indicate internal damage, requiring a comprehensive inspection or a complete transmission rebuild or replacement by a qualified technician. Always refer to the service manual for specific torque specifications and detailed procedures tailored to the 2020 Toyota Highlander.