what does it mean if the HVAC code B1240 shows up on my Toyota Highlander

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, basic hand tools (screwdrivers, socket set)
• Disconnect the vehicle battery to ensure safety.
• Allow the vehicle to cool down if it has been running.

2. Inspect Wiring and Connections

• Locate the solar sensor, typically found near the windshield.
• Sub-steps:
  • Remove the cover or panel to access the wiring harness.
  • Check for frayed wires, corrosion, or loose connections.
  • Repair or replace any damaged wiring or connectors.

3. Test the Solar Sensor

• Tools Required: Multimeter
• Sub-steps:
  • Disconnect the solar sensor connector.
  • Set the multimeter to the resistance (Ohms) setting.
  • Measure the resistance across the sensor terminals; refer to the vehicle service manual for the specified range.
  • If the resistance is out of specification, replace the solar sensor.

4. Clear Codes and Test System

• Reconnect the solar sensor and any components removed during inspection.
• Reconnect the vehicle battery.
• Use the OBD-II scanner to clear the B1240 code.
• Start the vehicle and test the HVAC system for proper function.