how to diagnose and fix P0700 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

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

2. Address Fluid Issues

• Check Fluid Level:
  • Remove the transmission dipstick (if equipped) and wipe it clean.
  • Reinsert, then remove again to check the fluid level; add fluid if low.
• Inspect Fluid Condition:
  • If the fluid is dark or has a burnt smell, it needs to be replaced.

3. Replace Transmission Fluid (if needed)

• Drain Old Fluid:
  • Place a drain pan under the transmission pan and remove the pan bolts.
  • Allow the fluid to completely drain.
• Replace Filter:
  • Remove the old transmission filter and install a new OEM filter.
• Install New Fluid:
  • Reinstall the transmission pan with a new gasket and torque to manufacturer specifications (usually around 10-12 ft-lbs).
  • Use the correct type of transmission fluid as specified in the owner’s manual (typically Toyota WS fluid).
  • Fill the transmission with the new fluid using a fluid pump until it reaches the proper level.

4. Repair or Replace TCM (if diagnosed)

• If the TCM was determined to be faulty during the diagnostic process, remove the old TCM by:
  • Disconnecting the battery.
  • Removing the TCM connectors.
  • Unscrewing the mounting screws and carefully removing the unit.
• Install the new TCM by reversing the removal steps, ensuring all connections are secure.

5. Clear Codes and Test

• Use the OBD-II scanner to clear the P0700 code.
• Perform a road test to ensure the transmission operates correctly and no codes reappear.