What is OBD, what OBD can do?

Most car owners have heard of OBD port but few know what it is and what it can do. They just see at the repair shop a mechanic diagnose the car by plugging a scan tool into the port, then the trouble codes are erased and the cleaned air damper stops a warning. However, the OBD port is not as mysterious as imagined. Car owners can become car geeks by knowing how to use it.

What is OBD?

OBD stands for On Board Diagnostics. When the car is running, it monitors the engine electronic control system and other electronic control modules. If there is something unusual, it will detect what the trouble is and store the DTC (Diagnostic Trouble Code) on the ECU (Electronic Control Unit). The DTC helps for car repair and maintenance. A mechanic can quickly locate the problem by reading the code with a scan tool, saving time for a repair.

The OBD port normally locates under the steering wheel, near the place of driver’s knee. Its actual position may differ in car models, but overall it is almost the same position.

The port uses a standard female 16-pin interface. The trapezoidal design is to avoid a wrong plug which may lead to a short circuit.

In early time, each manufacturer had its own system and signals, making it inconvenient for car maintenance. To solve this problem, SAE (the Society of Automotive Engineers) introduced OBD II standard in 1988.

As initially a system for monitoring exhaust gas emission, OBD developed to expand its range of monitoring all sensors of cars.

At first, OBD port took the K-line communication mode based on ISO protocol, which had been eliminated due to its low communication efficiency. With the development of technology, a new communication mode, CAN-BUS, becomes the mainstream. It also bases on ISO protocol, but is more extended. This protocol makes vehicle diagnostics easier. One diagnostic tool is able to diagnose vehicles by different manufacturers.

What OBD can do?

Display on-board computer data

As communication port of on-board monitoring system, OBD port can not only read trouble codes, but also provide all kinds of data on vehicles. Besides the data displayed on the dashboard, actually there are many more data stored in the on-board computer, such as fuel consumption, battery voltage, air-fuel ratio and so on.  Those data are not available for owners with low cost cars as there is no an on-board computer display equipped to show the data. Therefore, there are specialized on-board computer displays available on the market.

There are two kinds of those products.
1. Hand held scan tool

• Simple trouble code reader that can read only data of vehicle engine
• Advanced scan tool that has access to more data and functions

2. Wireless OBD adaptor + smartphone app

The wireless OBD adaptor reads data from the OBD port and transmits the data to smartphone by Bluetooth or Wi-Fi. And the data will be displayed to the user via smartphone app.

Enable more car functions by changing codes.

The electronic control system on modern cars allows adjusting the function of each control module by plugging into the OBD port. The most famous application on this field is the 5053 serious data link and VCDS system diagnostic software developed by Ross Tech. Most VW car owners love to use the tool to adjust the function of their cars. Due to different allocation and selling price, most functions related with car comfort are disabled by the manufacturer. But it is available by connecting with CAN-BUS of the car via OBD port.

Access and flash ECU and TCU

With the upgrade of hardware of on-board computer system, the ECU on modern cars is flashable. In this way, the manufacturers are able to update the ECU to meet different working environment. Some manufacturers even set TCU (Transmission Control Unit) to be flashable. Initially when the problem of the VW’s seven-speed DSG happened, the method of flashing TCU was taken to adjust some parameters of the DSG.

The refitting manufacturers see the convenience of flashing ECU and TCU, so they begin to provide those refitting projects. The power take-off on original cars is reserved due to the stability of ECU. By flash the ECU, the power take-off will be increased. With a TCU flash, the gearbox will be more sensitive and radical while shifting. All these benefits are available by connecting the data link with the computer and car via the OBD port.

In a word, though OBD is initially for monitoring the exhaust gas emission, it has developed to have more functions.