OBD-II and OneGauge

OBD-II, or On-Board Diagnostics version 2, is a communication system in modern vehicles that transmits various sensor readings and calculations for troubleshooting or diagnosis. It was originally created as part of the effort to reduce emissions, so most of the data transmitted concerns fuel and economy information.

Vehicles sold in the United States in 1996 and up are required by law to be fitted with an OBD-II system. At first there were a variety of ‘protocols’, or languages, used to transmit the information. In 2008, an standardized CAN-BUS communication method was required in all US vehicles. This newer communication is much after and faster than pre-2008 communication. Many vehicles between 2005 and 2008 upgraded early however (see this list for details).

Note that pre-2008 vehicles or engines without CAN-BUS will have slower communication (about 2-3x per second), so fast updating gauges like RPM will be slow to respond and the user will have noticeable lag. There are many workarounds for this, however, so please don’t hesitate to reach out and discuss options with us. CAN-BUS enabled OBD-II ports can communication many times faster (50-100x per second, at least) so lag is not an issue.

There is a long list of sensor data that is transmitted by OBD-II, but this varies by year, make, model, and engine. RPM, Coolant Temp, MAP (boost/vacuum), IAT, fuel trim (short and long term), TPS, and MAF are standard, but most vehicles transmit much more information. We can only guarantee that the readings in the previous list are transmitted to OneGauge; since other sensors often require manufacturer- or engine-specific codes (called PIDs) to be able to read the data, it can be difficult to access these readings. Other companies and apps that develop gauges typically pay expensive licensing fees to the major auto manufacturers for the rights to these codes, though they can occasionally be found on the internet. We have had some success in getting GM and Ford specific PIDs to work, but these are not guaranteed since they can vary by year/engine/make/model.

A few notes on OBD-II:

  • Most vehicles do not monitor Oil Pressure as part of the OBD system. We recommending adding an Oil Pressure sensor to get that reading on your OneGauge system.
  • OneGauge offers two types of OBD-II setups.
    • Wireless OBDII systems send data readings 2-5x per second, and while this is relatively fast, it may make the Speedometer and Tachometer readings seem lagged or slow. To avoid this, we recommend upgrading to either the GPS Speedometer option or external Tachometer (or, for best results, both) so that readings can come in more quickly.
    • Wired OBD-II connections read at 10-20x/second so these additional connections may not be necessary. For all pre-2008 vehicles installing a wired setup, it’s is the customer’s responsibility to confirm compatibility- to check older vehicles, use this website.