Using OBD2 Scan Codes to Diagnose Your Car’s Problems

If you are not yet sure of how to use OBD2 scan codes to analyze what is wrong with your car, here is a case study to help illustrate the process. In this example, the problem with the car is that it suffers from a faulty oxygen sensor. The oxygen sensor measures the amount of unburned oxygen in the tank and adjusts the air-to-fuel ratio accordingly. If the sensor is defective, then the car’s fuel consumption increases as it allows more fuel to be used than is needed. Let’s take a look at how OBD2 codes can help you detect and diagnose the problem.

obd2 scan codes

The first indicator that there is a problem is the Malfunction Indicator Light (MIL) goes on. Once this happens you connect your OBD2 scan codes reader to the data link connector (DLC) in your car to diagnose the problem. There are a number of codes it could bring up if your oxygen sensor is defective.

OBD2 Scan Codes P0138

If your OBD2 codes reader displays this code on the screen, it means that the rear heated oxygen sensor 2 (HO2S-2) is producing a weaker signal than the front one due to voltage of over 999 mV for more than two to four minutes, depending on the car model. Alternately, it could mean that there has been a short to the battery voltage in the circuit of HO2S-2. Hence, the fix could be to replace the O2 sensor or to repair the short.

OBD2 Scan Codes P0130

When this code comes up on the readers it indicates the opposite problem from the above. In this case, the voltage to the sensor was too low for too long a period of time. Although the problem in its early stages may have no symptoms other than the MIL being on, if it persists, signs such as black smoke emerging from the tail pipe, poor fuel economy and the engine dying could result. Apart from a defective O2 sensor, other causes could be corrosion or water damage in the connector, loose terminals, burnt wiring or holes in the exhaust that allow uncontrolled amounts of oxygen into the system. You can use a scan tool to diagnose the nature of the problem and make the appropriate repairs.

OBD2 Scan Codes and the DIY Car Owner

The example above highlights how a knowledgeable do-it-yourself can use scan codes to identify the nature of the car’s problem when the check engine light goes on. The definition of OBD2 scan codes can be looked up from specialized online look up sites or from a print diagnostic trouble code manual. If the second character of the diagnostic code is 1 then this indicates that it is a proprietary code used by a particular manufacturer, and you can find the definition in your user’s manual. If you have a high-end code reader, then it may conveniently display the definition of the OBD2 diagnostic codes flashed on the screen along with the code itself allowing you to see what the problem is at once.

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