How To Test OBD
On-board diagnostic systems are more sophisticated than ever. OBD2, a new standard introduced in the mid-'90s, provides almost complete engine control while also monitoring chassis, body and accessory devices. Computers may seem more complicated than oil and grease, but The Part Pros are here to help you test your system and locate any problems in the diagnostic network.
Remember, if you have any questions or if you're unsure of anything, feel free to contact the Parts-King.
Since all vehicles are not the same please refer to the manual supplied with the OBD2 code reader for vehicle specific instructions.
Is your vehicle compliant?
All cars and light trucks manufactured since late 1995 should be OBD2 compliant. Two factors will show if your vehicle is definitely OBD2 equipped:
There will be a note on a sticker or nameplate under the hood: "OBD2 compliant” There will be an OBD2 connector as shown below
Pin 2 - J1850 Bus Pin 4 - Chassis Ground Pin 5 - Signal Ground Pin 6 - CAN High (J-2284) Pin 7 - ISO 9141-2 K Line Pin 10 - J1850 Bus Pin 14 - CAN Low (J-2284) Pin 15 - ISO 9141-2 L Line Pin 16 - Battery Power
Safety comes first
Every vehicle is different. When it comes to maintenance and repairs, always follow the vehicle's owner's manual.
Safety should be your number one priority. Don't smoke, drink alcoholic beverages, or wear a necktie while working on the car. Watch out for hot objects, sharp instruments, hazardous materials and other potential safety hazards in and around your workspace.
Don't work with a Philips when the job calls for a flat. Substituting tools can compromise your safety or your vehicle's performance.
Finally, when the fun turns to frustration, or if the job requires specialized knowledge beyond your capabilities, please do not attempt it yourself. Talk to a professional mechanic or installer. The last thing we want is someone getting hurt.
Where is the connector located?
The connector must be located within three feet of the driver and must not require any tools to be revealed. Look under the dash and behind ashtrays.
Important info about OBD2
- Can diagnose/check engine problems in all CAN and OBD2 vehicles (1996 and newer) and many of the most popular OBD1 (1981 to 1995) vehicles.
- Features unique patented all-in-one screen display and LED display for quick emissions check
- Automatic refresh updates data every 30 seconds when connected to the vehicle - an easy way to verify repair completion.
- Code definition can be displayed in English, French and Spanish.
- Can be Flash updated with a standard Windows® PC.
- Features memory/battery backup for off-car review and analysis
Connecting the OBD2 Code Reader is as simple as locating the DLC connector. The DLC connector is usually found under the driver side (left side) of the dash. The cable attaches only one.
Reading the LCD display
- Before you start testing, take a good look at the LCD display. The illustration above explains what the various icons mean and how the DTC (Diagnostic Trouble Code) will be displayed. The unit is self-powered by three-AAA batteries and will let you know when they are running low. When connected/receiving power from the vehicle, the CAR Icon will display.
- The OB2 code reader is a very simple tool to use. Once it is connected, turn the power on. Once the ignition is switched to the on position, the code reader is checking the system for any stored DTCs. The meaning of each DTC can be found in the manual supplied with your code reader.
Example: the code reader displays a DTC PO309, Cylinder 9 misfire was detected.
P0298 Engine Oil Over Temperature
P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0304 Cylinder 4 Misfire Detected
P0305 Cylinder 5 Misfire Detected
P0306 Cylinder 6 Misfire Detected
P0307 Cylinder 7 Misfire Detected
P0308 Cylinder 8 Misfire Detected
P0309 Cylinder 9 Misfire Detected
P0310 Cylinder 10 Misfire Detected
P0311 Cylinder 11 Misfire Detected
- Once you know what the problem is, you have to determine what's causing it. In this case the intake manifold gasket was faulty. Once the repairs have been made, it is time to clear the DTC and check the system to verify the repair.
Clearing the diagnostic trouble code (DTC)
Clearing the DTC is very simple:
- Press the ERASE button on the code reader. A message will display on the screen; "SURE" for confirmation.
- If you wish to clear the DTC press and hold down the ERASE button again until a message appears on the screen "DONE".
- If you did not wish to clear the codes and hit Erase by mistake at the screen message "SURE" simply press the link button to return without erasing any DTCs.
- When you clear the DTC(s) from the PCM (Power train Control Module) you also clear ALL of the other gathered information that the PCM has collected, including Freeze Frame, Drive Cycle data, manufacture specific enhanced data and everything stored in memory is erased - just like if you cleared the Cache files on your PC.
- The vehicle's PCM will need to re-learn the information that was erased. Don't be alarmed!! This is easily accomplished just by driving the vehicle. All you have to do is get driving.