Skip the auto shop - Our mechanics make house calls

How Can I Tell If the OBD System Is Working Correctly?

CheckEnginglightDash

Today’s cars are far more sophisticated than they once were, and they require a computer to monitor and manage the various systems so that everything works together properly. This also gives you the means to determine if there’s something going wrong with your car. The OBD II system (On Board Diagnostic) is a system that allows a mechanic to communicate with your car’s computer and pull trouble codes in many situations. These codes tell the mechanic where the trouble is, but not necessarily what the actual problem is.

How to tell if the OBD is working

Determining if your OBD system is working is actually very simple.

Start with the engine off. Turn the key to "on," and then run so that the engine cranks. Watch the dash during this time. The Check Engine Light should flash on, and stay on for a brief period. It should then turn off. The brief flash on is the signal that the system is up and running, and ready to monitor your vehicle during operation.

If the Check Engine Light comes on and stays on, then there’s a trouble code (DTC) stored in the computer that indicates a fault somewhere in the engine, the transmission or the emissions system. This code should be checked by a mechanic so that an accurate repair can be made.

If the Check Engine Light does not flash and turn off (or if it never comes on at all), it’s a sign that there is something wrong with the system, and it must be checked by a professional mechanic.

Your vehicle will not pass annual testing without an operable OBD system, and you will also have no way of knowing if something is wrong with the vehicle.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
Veteran and Military Driver Laws and Benefits in New Mexico
The state of New Mexico offers a number of benefits and perks for those Americans who have either served in an Armed Forces branch...


Related questions

Q: Do all cars have an OBD system?

Virtually all vehicles from the 1987 model year to the present day have an OBD system. Some earlier model year vehicles, but not all, have some semblance of an OBD system. However, their diagnostic abilities are severely limited. There are...

Q: What are the most common reasons my car won't start?

Be sure any engine immobilizer system (security system) is not activated, thus preventing the car from starting. "New" batteries are not necessarily fully charged when you buy them over the counter. Consequently, it has to be confirmed that the battery...

Q: car cranks but doesn't start

When this situation occurs, the first thing I look for is checking the fuses or electrical relays to the ECU. In general, the most common cause of being unable to connect to the scanner or to the ECU is caused...