how to diagnose P0700 code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools and safety equipment.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the vehicle is on a level surface and secured with jack stands if needed.

2. Address Transmission Fluid Issues

• Check Fluid Level:

  • Remove the transmission dipstick.
  • Wipe clean and reinsert, then check the fluid level; add fluid as necessary (use Toyota ATF WS).

• Inspect Fluid Condition:

  • If the fluid is dark or has a burnt smell, consider a transmission fluid flush and replace with fresh fluid.

3. Inspect and Repair Wiring and Connectors

• Visual Inspection:

  • Locate the transmission wiring harness.
  • Check for frayed wires, corrosion, or loose connectors; repair or replace as necessary.

• Connector Cleaning:

  • Use electrical contact cleaner on connectors and ensure a snug fit after cleaning.

4. Test and Replace TCM (if necessary)

• TCM Testing:

  • Use a multimeter to check power and ground at the TCM.
  • If the TCM is faulty, remove it by unscrewing the mounting bolts and disconnecting the wiring harness.

• TCM Replacement:

  • Install the new TCM and ensure all connections are secure.
  • Reconnect the negative battery terminal.

5. Clear Codes and Test Drive

• Use the OBD-II scanner to clear the P0700 code and any other related codes.
• Perform a test drive to ensure proper transmission operation and check for reoccurrence of the code.