how to troubleshoot transmission slipping in my Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is turned off.
• Tools Required: OBD-II scanner, socket set, transmission fluid gauge, torque wrench, fluid catch pan.

2. Inspect and Replace Transmission Fluid

1. Check Fluid Level
   • Start the engine and let it warm up to operating temperature.
   • With the vehicle in park, remove the transmission dipstick and wipe it clean.
   • Reinsert the dipstick, then remove it again to check the fluid level; it should be between the "full" and "add" marks.
2. Replace Fluid if Needed
   • If low, add the recommended transmission fluid (Toyota ATF WS) until it reaches the proper level.
   • If the fluid is dark or has a burnt smell, replace it:
     • Remove the transmission pan bolts using a socket set.
     • Carefully lower the pan and allow old fluid to drain into the catch pan.
     • Replace the filter if applicable and clean the pan.
     • Install a new gasket and torque the pan bolts to the manufacturer’s specifications.
     • Refill with new fluid through the dipstick tube.

3. Electrical Check

1. Inspect Wiring
   • Disconnect the battery before working on electrical systems.
   • Visually inspect the wiring harness connected to the transmission control module for any signs of damage or corrosion.
   • Use a multimeter to check continuity in the wires; repair or replace as necessary.

4. Pressure Testing

1. Check Transmission Fluid Pressure
   • Attach a transmission fluid pressure gauge to the test port (if equipped).
   • Start the engine and check the pressure at idle and during acceleration; compare it to manufacturer specifications.
   • If pressure is low, further internal inspection may be necessary.

5. Reassemble and Test

1. Reassemble Components
   • Reconnect any electrical connectors and lower the vehicle.
   • Start the vehicle and let it run for a few minutes to circulate the new fluid.
   • Test drive the vehicle to confirm that the slipping issue has been resolved.