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

Solution

1. Preparation

• Gather tools: OBD-II scanner, multimeter, socket set, torque wrench, fluid catch pan, and replacement transmission fluid.
• Disconnect the negative battery terminal to ensure safety while working on the electrical components.

2. Check and Replace Transmission Fluid

• Inspect Fluid Level and Condition
  • Remove the transmission dipstick and check the fluid level with the engine running.
  • If the fluid is low, add the recommended type of transmission fluid (consult the owner’s manual for specifications).
• Change Fluid if Contaminated
  • If the fluid is dark or has a burnt smell, drain the transmission fluid into a catch pan.
  • Replace the fluid filter if applicable, following manufacturer instructions.

3. Inspect and Repair Wiring/Connectors

• Visual Inspection
  • Examine the wiring harness and connectors to the TCM for signs of wear or damage.
• Repair/Replace Components
  • Repair any damaged wires or replace connectors as necessary. Ensure all connections are secure.

4. Test and Replace Transmission Control Module (if necessary)

• Testing
  • Using a multimeter, check the voltage and ground connections to the TCM.
  • If the TCM is not functioning correctly, consult the service manual for replacement procedures.
• Replacement
  • Remove the old TCM by disconnecting the wiring harness and unscrewing the module from its mounting.
  • Install the new TCM, reconnecting the wiring harness securely and torqueing to manufacturer specifications.

5. Reassemble and Finalize

• Reconnect the negative battery terminal.
• Double-check all connections and fluid levels before closing the hood.