why does my Honda Accord 10th Generation (2018-2022) dashboard show a U0121 code?

Learn how to diagnose and fix U0121 electrical communication issues in Honda Accord (2018-2022). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative terminal of the battery to ensure safety.

2. Inspect Wiring and Connectors

• Tools Required: Multimeter, wire brush, connector cleaner
• Inspect the wiring harnesses for the control modules associated with the U0121 code.
  • Look for frayed wires, broken connectors, or signs of wear.
  • Clean any corroded connectors with connector cleaner and ensure a secure fit.
• Use a multimeter to test for continuity in the wiring between the control modules.

3. Check Ground Connections

• Inspect the ground points related to the affected modules.
• Clean any corroded grounds and ensure they are tightly secured.
• Use a multimeter to verify continuity from the ground point to the battery negative terminal.

4. Test Fuses and Battery

• Tools Required: Fuse tester
• Check the fuses associated with the control modules.
  • Replace any blown fuses with the correct rating.
• Test the battery voltage; it should be around 12.6 volts when fully charged.
  • If the battery is weak or old, replace it with a new one.

5. Reconnect and Test

• Reconnect the negative terminal of the battery.
• Clear the U0121 code using the OBD-II scanner and test drive the vehicle.
• Monitor for any reoccurrence of the code or related symptoms.