what causes my Toyota Highlander Third Generation (2014-2019) transmission to slip when shifting

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

3 min read

518 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 in Toyota Highlander (2014-2019). Step-by-step guide with symptoms, diagnostic steps, 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 systems.
•Ensure the vehicle is securely raised and supported before working underneath.

Symptoms

•Slipping sensation during gear changes
•Delayed engagement when shifting from park to drive or reverse
•Unusual engine revving without corresponding acceleration
•Check engine light illuminated
•Harsh or rough shifting

Diagnostic Steps

1
Scan the vehicle for error codes using an OBD-II scanner to check for transmission-related codes.
2
Inspect the transmission fluid level and condition, checking for contamination or burnt smell.
3
Examine the transmission fluid filter for clogs or restrictions.
4
Inspect the transmission control module (TCM) for electrical issues or faulty connections.
5
Check the condition and operation of the throttle position sensor (TPS) and vehicle speed sensor (VSS).
6
Road test the vehicle to reproduce the slipping issue under various driving conditions.

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
•Socket set
•Multimeter
•Fluid pump
•Torque wrench

Parts Required

•Toyota ATF WS transmission fluid
•Transmission filter
•Gasket for transmission pan
•TCM (if replacement is required)

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Diagnostic Steps

1
Scan the vehicle for error codes using an OBD-II scanner to check for transmission-related codes.
2
Inspect the transmission fluid level and condition, checking for contamination or burnt smell.
3
Examine the transmission fluid filter for clogs or restrictions.
4
Inspect the transmission control module (TCM) for electrical issues or faulty connections.
5
Check the condition and operation of the throttle position sensor (TPS) and vehicle speed sensor (VSS).
6
Road test the vehicle to reproduce the slipping issue under various driving conditions.

Solution

1. Preparation

Gather necessary tools and parts.
Disconnect the negative battery terminal for electrical safety.
Raise the vehicle securely on jack stands.

2. Check and Replace Transmission Fluid

Tools Required: Socket set, fluid pump, container for fluid.
Remove the transmission fluid dipstick and check the fluid level.
If low, add the appropriate transmission fluid (Toyota ATF WS).
If fluid is burnt or contaminated, proceed to replace it:
1. Drain Fluid: Remove the transmission drain plug and let the old fluid drain into a container.
2. Replace Filter: Remove the transmission pan by unscrewing the bolts, then replace the filter inside.
3. Reinstall Pan: Clean the pan, apply a new gasket, and reinstall it with proper torque specifications (consult manufacturer specs).

3. Inspect and Fix Electrical Components

Tools Required: Multimeter, wire connectors.
Check the wiring harness and connectors of the TCM for signs of wear or corrosion.
Test the TPS and VSS with a multimeter to ensure they are functioning within specifications. Replace if faulty.

4. Reprogram or Replace TCM

If electrical components are functioning but slipping persists, consider reprogramming or replacing the TCM:
1. Use a compatible scan tool to reprogram the TCM according to manufacturer specifications.
2. If replacement is necessary, remove the old TCM and install the new one, ensuring all connections are secure.