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General Info about On-Board Diagnostics (OBDII)

What is OBDII?

On-board diagnostics version II (OBDII) is a system that the Society of Automotive Engineers (SAE) developed to standardize automotive electronic diagnosis. Beginning in 1996, most new vehicles sold in the United States were fully OBDII compliant.

The OBDII system is designed to monitor emission control systems and key engine components by performing either continuous or periodic tests of specific components and vehicle conditions. When a problem is detected, the OBDII system turns on a warning lamp (MIL) on the vehicle instrument panel to alert the driver typically by the phrase of “Check Engine” or “Service Engine Soon”. The system will also store important information about detected malfunction so that a technician can accurately find and fix the problem. Here are the 3 key areas of information:

1)      Whether the Malfunction Indicator Light (MIL) is commanded ON or OFF;

2)      Which, if any, Diagnostic Trouble Codes (DTCs) are stored;

3)      Readiness Monitor Status

 

Does my car have OBDII?

All cars and light trucks built and sold in the United States after January 1st 1996 were required to be OBDII equipped. In general, this means all 1996 model year cars and light trucks are compliant, even if built in late 1995.

Two factors will show if your vehicle is definitely OBDII equipped:

  1. Where will be an OBDII connector
  2. There will be a sticker or notice under the hood stating the vehicle is OBDII compliant

obd-certified-emission-sticker.gif

 

Data Link Connector (DLC)

What is a DLC?

The data link connector (DLC) allows the scan tool to communicate with the vehicle’s computer(s). Before OBDII, manufacturers used different DLC’s to communicate with the vehicle. Use the proper DLC adapter cable to connect the Scan Tool to the vehicle. Also, the vehicle’s DLC may be found in several different places and have many different configurations.

dlc.jpg

Where is the connector located?

The connector must be located within 3 feet of the driver and must not require any tools to be accessed. Look under the dash near the steering wheel and pedals.

obdii-location.jpg 

Diagnostic Trouble Codes (DTCs)

DTCs are codes that are stored by the on-board computer diagnostic system in response to a problem found in the vehicle. They are used to help determine the cause of a problem or problems with a vehicle. DTCs consist of a five-digit alphanumeric code such as P0202

diagnostic-trouble-codes-dtcs.jpg

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