How to fix OBD connection [OBD no communication]

When your OBD isn’t working, the first step is to determine if the problem lies with your car or the scan tool. Test the scan tool on another car:

• If it works on another car, the issue is with your car.
• If it doesn’t work, the problem is likely with your scan tool.

Why Won’t My OBD2 Scanner Work?

In my experience, almost always when my scanner could not work it was because of this thing. I forgot to turn on the ignition so the scanner could not communicate with control modules.

Basics to Check First

1. Ignition/Engine ON: Ensure the ignition is ON or the engine is running. For keyless vehicles, press the start button once to turn on the ignition.

1. No OBD System but OBD2 Port

Some cars have an OBD2 port without the actual system due to cost-cutting. Verify the presence of the OBD2 system:

• Check the back of the OBD2 port for connected cables.
• Use another OBD scanner to confirm.

2. ECM in “Hung” Mode or Blown

The ECM can be in a non-communicative state (“hung” mode). If blown, the engine runs rough.

• Reset the ECM:
  • Disconnect battery leads for 15 minutes.
  • Press the brake pedal to discharge capacitors.
  • Note: Disconnecting the battery may require resetting the radio and other systems.

3. OBD Port Does Not Have Power

Use a digital multimeter to check for power:

• Positive Lead (Red): Pin 16 (Battery Power)
• Negative Lead (Black): Pin 4 (Ground)
• Voltage Setting: 15V or 20V (not less than 12V)
• No Power: Replace the OBD port fuse.

4. Faulty OBD2 Scanner

Test the scan tool on another car:

• Doesn’t Work: Contact the seller for a fix or replacement if under warranty.

5. External Device Problems (Bluetooth Adapter)

Check compatibility with your external device (smartphone, tablet, or laptop):

• Compatibility Issues: Research and ensure compatibility with your operating system. Many cheap adapters are not compatible with iOS.

6. Car’s OBD2 System Communication Issue

This is a complex problem involving damaged wiring or the CAN bus system:

• Look for YouTube videos or other resources specific to your car model/brand for troubleshooting tips.

7. Scan Tool Not Compatible with Your Car

Not all scan tools work with all car brands:

• Check the scan tool description and reviews for compatibility information.