how to fix P0700 transmission control system malfunction in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the vehicle is on a level surface and safely secured with jack stands if necessary.

2. Inspect Transmission Fluid

• Remove the transmission dipstick and check the fluid level and condition.
• If the fluid is low, add the appropriate type of ATF as specified in the owner's manual.
• If the fluid is contaminated or burnt, a transmission fluid change may be necessary.

3. Inspect Wiring and Connectors

• Visually inspect the wiring harness connected to the transmission control module.
• Look for any frayed wires, loose connections, or corrosion.
• Repair or replace any damaged wires or connectors identified during the inspection.

4. Test the Transmission Control Module

• Using a multimeter, check the voltage at the TCM harness connectors.
• Ensure that the TCM is properly grounded and receiving the correct voltage (usually between 12-14 volts).
• If readings are outside the specification, further investigate the power supply or consider replacing the TCM if it is faulty.

5. Reassembly and Testing

• Reconnect all wiring and connectors securely.
• Reconnect the negative battery terminal.
• Clear the fault codes using the OBD-II scanner.
• Start the vehicle and conduct a test drive to ensure the transmission operates smoothly.