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

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

3 min read

564 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 Toyota Highlander (2014-2019). Step-by-step guide with symptoms, diagnostics, and repair instructions.

Affected Component

Transmission

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical components.
•Allow the engine and transmission to cool before servicing.

Symptoms

•Transmission engages late or early when shifting gears
•Unusual revving of the engine without corresponding acceleration
•Sudden loss of power during acceleration
•Check engine light illuminated
•Fluid leaks under the vehicle
•Transmission overheating warning light may appear

Diagnostic Steps

1
Scan the vehicle's OBD-II system for any error codes related to the transmission.
2
Check the transmission fluid level and condition; look for signs of contamination or burning smell.
3
Inspect the transmission fluid filter for clogs or blockages.
4
Examine the transmission wiring harness and connectors for any signs of damage or corrosion.
5
Test the transmission solenoid operation using a multimeter to ensure it’s functioning properly.
6
Perform a road test to replicate the slipping issue while monitoring engine RPM and speed.

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
•Transmission funnel
•Drain pan
•Socket set
•Torque wrench

Parts Required

•Transmission fluid
•Transmission filter
•Transmission pan gasket
•Transmission solenoid (if faulty)

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Diagnostic Steps

1
Scan the vehicle's OBD-II system for any error codes related to the transmission.
2
Check the transmission fluid level and condition; look for signs of contamination or burning smell.
3
Inspect the transmission fluid filter for clogs or blockages.
4
Examine the transmission wiring harness and connectors for any signs of damage or corrosion.
5
Test the transmission solenoid operation using a multimeter to ensure it’s functioning properly.
6
Perform a road test to replicate the slipping issue while monitoring engine RPM and speed.

Solution

1. Preparation

Gather necessary tools and parts.
Ensure the vehicle is parked on a level surface and the engine is cool.
Disconnect the negative battery terminal to prevent electrical shorts.

2. Check and Replace Transmission Fluid

Tools Required: Transmission funnel, drain pan, socket set.
Remove the transmission drain plug and allow the old fluid to drain completely into the pan.
Replace the drain plug and torque it to the manufacturer's specification.
Refill with new transmission fluid as per the vehicle's specifications (check owner's manual for type and quantity).

3. Inspect and Replace Transmission Filter

Tools Required: Socket set, pick tool, gasket scraper.
Remove the transmission pan bolts and carefully lower the pan.
Remove the old transmission filter from its mounting.
Install the new filter, ensuring it is securely in place.
Clean the gasket surface on the pan and replace the pan with a new gasket, tightening bolts to the manufacturer's torque specifications.

4. Test Transmission Solenoid

Tools Required: Multimeter, wiring diagram.
Disconnect the solenoid connector.
Set the multimeter to the resistance setting and measure the resistance across the solenoid terminals.
Compare the reading to the manufacturer's specifications; replace if out of range.

5. Reconnection and Testing

Reconnect the negative battery terminal.
Start the vehicle and check for leaks around the transmission pan and solenoid.
Take the vehicle for a test drive to ensure the slipping issue has been resolved.