why does my Toyota Highlander Third Generation (2014-2019) transmission slip when I accelerate

Toyota Highlander Third Generation (2014-2019)

Error Codes

3-5 hours

Time

medium

Difficulty

high

Severity

3 min read

509 words

⚠️ Safety Warning

This issue requires immediate attention. If you are not experienced with automotive repairs, consult a professional mechanic. Working on critical systems can be dangerous.

Problem Statement

Learn how to diagnose and fix transmission slipping issues in the 2014-2019 Toyota Highlander. Step-by-step guide with symptoms, diagnostics, and repairs.

Affected Component

Transmission

Estimated Time

3-5 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect battery before working on electrical systems.
•Allow engine to cool before opening the transmission system.

Symptoms

•Transmission slips when accelerating
•Delayed engagement when shifting from park to drive
•Unusual noises (grinding or whining) from the transmission
•Check engine light illuminated
•Increased engine RPM without corresponding acceleration
•Poor fuel economy

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to check for transmission-related fault codes.
2
Inspect the transmission fluid level and condition (color, odor).
3
Check for any visible leaks around the transmission and associated lines.
4
Test the transmission solenoids for proper operation using a multimeter.
5
Inspect the transmission filter for clogs or contamination.
6
Evaluate the condition of the torque converter.

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
•Multimeter
•Socket set
•Torque wrench
•Funnel
•Drain pan

Parts Required

•Transmission fluid (Toyota ATF WS)
•Transmission filter
•Gasket for transmission pan
•Replacement solenoids (if faulty)

Related Faults

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to check for transmission-related fault codes.
2
Inspect the transmission fluid level and condition (color, odor).
3
Check for any visible leaks around the transmission and associated lines.
4
Test the transmission solenoids for proper operation using a multimeter.
5
Inspect the transmission filter for clogs or contamination.
6
Evaluate the condition of the torque converter.

Solution

1. Preparation

Gather tools and parts.
Ensure the vehicle is on a level surface and the engine is cool.
Disconnect the battery to prevent electrical shorts during repair.

2. Check and Replace Transmission Fluid

Tools Required: Funnel, drain pan, socket set, torque wrench.
Remove the transmission pan bolts using a socket wrench.
Carefully lower the pan and allow the old fluid to drain into the pan.
Inspect the magnet in the pan for metal shavings, indicating wear.
Clean the pan and replace the transmission filter.
Reinstall the pan using a new gasket and torque bolts to the manufacturer's specifications (typically around 8-10 ft-lbs).
Refill the transmission with the correct type and amount of fluid (Toyota ATF WS).

3. Test Transmission Solenoids

Tools Required: Multimeter.
Locate the transmission control module and unplug the electrical connectors from the solenoids.
Use the multimeter to test the resistance of each solenoid; compare readings to specifications in the service manual.
Replace any faulty solenoids with new parts.

4. Inspect Torque Converter

Tools Required: Torque wrench, transmission jack.
If previous steps do not resolve the issue, consider removing the transmission to inspect the torque converter.
Check for signs of wear or damage; replace if necessary.