why does my Volvo XC90's engine light and traction control light stay on

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.

2. Retrieve and Analyze Error Codes

• Connect an OBD-II scanner to the diagnostic port.
• Turn the ignition to the "On" position without starting the engine.
• Retrieve the stored error codes and note them for reference.

3. Inspect and Replace Faulty Sensors

• Based on the error codes, identify which sensors may need inspection or replacement.
  • For TPS: Remove the electrical connector and use a multimeter to check resistance.
  • For wheel speed sensors: Inspect wiring and connectors; replace if damaged.
• If faulty, replace the sensor following the manufacturer’s specifications.

4. Check and Repair Wiring

• Inspect the wiring harness leading to the ECU and traction control system.
• Look for frayed wires, corrosion, or loose connections.
• Repair or replace any damaged wiring as necessary, ensuring secure connections.

5. Clear Error Codes

• After replacing any faulty components, reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the error codes.
• Start the engine and check if the warning lights remain illuminated.