What is OBDII?

On-board diagnostics is a vehicle's computer system that makes sure the emissions system is working and that the vehicle isn't excessively polluting. It tests the vehicle's emission control system while driving.

How are vehicles OBDII tested?

An emissions repair technician attaches a cable to the vehicle's computer to see if the emissions system is working or not. If the emissions parts work, the vehicle will pass. If they don't then the vehicle fails and needs to be repairs.

A vehicle will also fail if Readiness Monitors are not set to "Completed".

What are Diagnostic Trouble Codes (DTC)?

When a vehicle's computer identifies a problem with a part of the emissions control system it stores a Diagnostic Trouble Code (DTC). The state emissions inspection report will list codes that cause your vehicle to fail the inspection. A trained repair technician can read these codes to figure out the problem. A code alone does not mean a part should be replaced, repairs should only be done after a professional diagnosis.

The DTCs that cause a fail must be repaired in order to pass the emissions inspections.

What are the advantages of OBDII testing?

OBDII saves you time and money. It finds problems quickly, even ones that aren't visible, before they get costly.

How are drivers alerted when OBDII finds a problem?

The OBDII lights the malfunction indicator lamp (MIL), commonly known as the the Check Engine or Service Engine light.

Does my warranty cover OBDII repairs?

Check your vehicle owner's/warranty manual for warranty coverage information.

Federal law requires that warranties for 1995 and newer vehicles cover:

  • Emissions-control systems for two years or 24,000 miles, whichever comes first.
  • On-board computer and catalytic converter eight years or 80,000 miles.

Many auto manufacturers provide extended warranty.