my Toyota Highlander Third Generation (2014-2019) transmission slips when shifting

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

3 min read

558 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 a 2014-2019 Toyota Highlander. Step-by-step guide with diagnostic procedures and repair instructions.

Affected Component

Transmission

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

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

Symptoms

•Transmission slips when shifting gears
•Unusual engine revving without acceleration
•Harsh or delayed shifting
•Check engine light illuminated
•Fluid leakage under the vehicle
•Burning smell from the transmission area

Diagnostic Steps

1
Scan the vehicle's onboard computer for any error codes using an OBD-II scanner.
2
Inspect the transmission fluid level and condition (color and smell).
3
Check for any visible leaks around the transmission pan and seals.
4
Inspect the transmission filter for blockages or contamination.
5
Test the operation of the transmission control module (TCM) and related sensors.
6
Perform a road test to replicate slipping and note specific conditions (e.g., engine temperature, 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
•Socket set
•Transmission fluid pump
•Drain pan
•Funnel
•Multimeter

Parts Required

•Transmission fluid (specific to Toyota specifications)
•Transmission filter
•Transmission pan gasket
•Transmission control module (if applicable)

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Diagnostic Steps

1
Scan the vehicle's onboard computer for any error codes using an OBD-II scanner.
2
Inspect the transmission fluid level and condition (color and smell).
3
Check for any visible leaks around the transmission pan and seals.
4
Inspect the transmission filter for blockages or contamination.
5
Test the operation of the transmission control module (TCM) and related sensors.
6
Perform a road test to replicate slipping and note specific conditions (e.g., engine temperature, speed).

Solution

1. Preparation

Gather tools and parts required for the repair.
Ensure the vehicle is parked on a flat surface and the parking brake is engaged.
Disconnect the battery to prevent electrical shorts.

2. Check and Replace Transmission Fluid

Tools Required: Transmission fluid pump, socket set, drain pan, funnel.
Sub-steps:
1. Remove the transmission dipstick and check fluid level; if low, proceed to drain and replace.
2. Place a drain pan under the transmission pan and remove the pan bolts using a socket set.
3. Allow the old fluid to drain completely and inspect for metal shavings or debris.
4. Clean the transmission pan and magnet thoroughly.
5. Replace the filter if necessary; remove the old filter and install the new one.
6. Reinstall the transmission pan with a new gasket and torque bolts to manufacturer specifications (usually 8-10 ft-lbs).
7. Refill the transmission with the appropriate type and amount of fluid as specified in the owner's manual.

3. Inspect and Replace Transmission Control Module (if necessary)

Tools Required: OBD-II scanner, socket set, multimeter.
Sub-steps:
1. If error codes indicate TCM issues, locate the module (usually under the dashboard or near the transmission).
2. Disconnect the battery again for safety.
3. Remove any covers or brackets securing the TCM.
4. Disconnect the wiring harness from the TCM and inspect for damage.
5. If necessary, replace the TCM with a new unit and reconnect the wiring.
6. Reconnect the battery and clear any error codes from the system.