Posted by Sponsored Post Posted on 28 January 2021

What Is OBD and OBD-II?

Ask most people which two machines built in the 20th century, and they’ll probably tell you “cars” and “computers.” So, it should come as no surprise that the two would collide at some point, like a train full of calculators crashing into a pile of aluminum cans. While some – like Granddad – might lament this as an unwelcome complication, the fact is that computers have made the modern automobile more powerful, versatile, efficient, and easier to work on than ever before. And odds are pretty good that if Grandad read that last sentence, he’d probably laugh himself into a hernia. But the Onboard Diagnostics used in every automobile produced today make this statement no laughing matter.

Onboard Diagnostics helps prevent car accidents. Remember even minor accidents can cause thousands in repair costs. Getting affordable car insurance under $50 a month plans can help you save money and keep more money in your pocket.

Computer self-diagnostics showed up in the late 1970s and early 1980s; not explicitly as a means to assist mechanics, but rather to assist in maintaining emissions compliance. Manufacturers, through the automobile’s early computerized era, were free to use whatever programming language they wished, which meant that mechanics and emissions techs had to have a different computer and scanner for every brand of automobile out there. This made for a huge mess and a massive buy-in cost for any government or private institution interested in emissions testing.

Onboard Diagnostics, Series II

In early 1996, the Federal government mandated the adoption of a standardized system, with a standard programming language that any scanner could read. Onboard Diagnostics, Series II was an entirely different animal than its predecessor both in terms of hardware and software; think of the difference between an Atari and a Playstation II, and you’re in the ballpark. 

Apart from hardware changes like standardized adapters and locations, OBD-II requirements included a second oxygen sensor to monitor the catalytic converter and the use of the standardized OBD-II programming code. When the computer detects a problem, it turns on your “check engine” or “service engine soon” light. At that point, you plug a scanner into the OBD-II port. You can often have this service performed for free at major chain auto parts stores, which will save you between $30 and $200 over purchasing one. Or: a number of companies sell connectors with OBD-II plugs on one side and a USB plug on the other, and the software needed to network your laptop to the car’s computer, giving you most of the capabilities of a manufacturer’s scanner a fraction of the professional scanner’s cost.

OBD Codes

The scanner will spit out a code that looks like this: P0175, P0028, or P0385. The code breaks down like into four sections: P – 0 – 1 – 75. The first character refers to the system:

  •  “P”- powertrain
  •  “B”- Body
  • “C” – Chassis
  • “U” – Undefined

The first number is either a “0” or a “1,” which marks it – respectively – as either a generic code readable by any standard OBD-II scanner, or a manufacturer-specific code that a generic scanner probably picks up. By law, anything related to the engine’s emissions must be a “0” code, readable by a standard scanner. Manufacturers reserve the right to charge you for reading “1” series codes at the dealership or to charge whatever they want to for a manufacturer-licensed scanner. 

The second one-digit number denotes the subsystem, starting at “1” for fuel or air emissions management, and running through “8” for a transmission fault. Numbers “9” and “0” are reserved for special purposes or future sub-systems. 

The last two-digit number is the “serial number” of a specific fault within a sub-system, and it’s what tells you exactly what’s wrong with the car. All told, there are about 8,000 possible OBD-II code combinations, which is why most scanners have a built-in index and will display not only the fault code but what it corresponds to on the general code chart.

If you think that charging to read manufacturer codes is dastardly, then you’ll want to sit down for this one. Not only will a generic scanner not pick up a 1-series manufacturer code, but the manufacturer can also program the computer to display the wrong 1-series or generic code on a generic scanner. So, the computer could trigger a check engine light because of a bad lock-up torque converter, but it might tell the generic scanner that the problem is a bad throttle position sensor. So, you buy a new TPS and install it, only to find that the code is still there, and there it will stay until you pay a dealer to pull the codes. Or, somewhat less evilly, the computer could be programmed to display a generic code that wasn’t assigned to anything at the date of manufacture. So, if you get a code that doesn’t correspond to anything in the charts, at least you’ve got a pretty good idea that it’s a 1-series code in hiding. Which isn’t as bad as giving you the wrong code.

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