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Almost any car engine manufactured since 1997 will have on-board diagnostics, either the OBD1 or more recently the OBD2 standard which provides a standard for protocols, standard message codes and a standard connector which is universal across all engines (there are different pinouts used but newer readers can usually read them all), plus the ability for manufacturers to add their own fault codes where applicable. There is also telemetry available from the engine sensors which can be read to diagnose engine health, for example air flow and inlet air temperature, engine coolant temperature, etc.

I am well aware that the vast majority of aviation pistons are completely mechanical, but for the small percentage of electronically controlled engines that are out there is there any such standard? Do they use OBD2, another common standard, or are they all proprietary?

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    $\begingroup$ "OBD2 standard which provides a standard protocol, standard messages and a standard connector which is universal across all engines" Having worked on OBD2 vehicles, I can tell you that it is not universal. Domestics have a few protocols, European cars seem to standardize on CAN (ISO15765). All told there are a lot, J1850 PWM, J1850 VPW, ISO9141-2, ISO14230-4, ISO15765-4/SAEJ2480. There are at least 2 types of "standard" connectors as well. There are "standard" PID/PGN's but they are hit or miss if they are implemented in favor of the manufacturer specific one... $\endgroup$ – Ron Beyer Aug 19 '20 at 12:28
  • $\begingroup$ OBD1 had many connectors, OBD2 has one, although there are different pinouts for it. These are well understood enough that there are readers that work with them all, and they are cheap and (relatively) easy to use. I don't think it's useful to go into detail on the protocols that are in use in my question, the point is to find out whether automotive systems are in use, or whether they use a different system. $\endgroup$ – GdD Aug 19 '20 at 12:42
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    $\begingroup$ @RonBeyer By US law, 2008+ vehicles must present a CAN interface. So it has been universal for over a decade. $\endgroup$ – user71659 Aug 19 '20 at 18:21
  • $\begingroup$ @user71659, yes and no. There is a specified small set of diagnostic messages over CAN that are required for emissions and general engine health check, but that is a tiny fraction of what the vehicle actually provides, the rest being vehicle-specific using various standards as a base. $\endgroup$ – Jan Hudec Mar 17 at 22:04
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OBD systems were introduced by law in the 80s to reduce / control emissions, so it originated as a method to determine fault with emissions control systems. However, it was refined enough to monitor and control in real time engine and powertrains sytems in further iterations. Keep in mind that the OBDI / OBDII is a protocol that is run on the CANBUS network, which is important to remember that these two are separate entities (CANBUS can run several different protocols, as Ron Beyer had stated). Other networks such as the LINbus for Audi/VW/BMW run different protocols but still work in a similar fashion.

From my military aircraft maintenance experience (from way back), our systems ran on the 1553 databus, which linked all systems together (nav, comms, AP/FD, etc) and is essentially the CANBUS equivalent. I believe Civil aircraft used the ARINC429 system, however I cannot confirm. For the protocol side, many aircraft (though mainly helicopters) use the Health Usage Monitoring System (HUMS), which provides the OBDII equivilant (more or less) to report back on engine condition, conditional maintenance, operation, etc.

So to make a short story long, there area a few standaridzed networks that aircraft use, however so far there is no standard protocol for all engines. Keep in mind that car manufacturers design and build the system as a whole in-house (chassis, powerplant and drivetrain), so it is not an issue to have all the systems integrate in a relatively simple manner), where airframes are generally designed by a company that will use a powerplant designed and built by a different manufacturer (or perhaps event the same airframe could have different engine variants from different companies), which makes standardization increasingly difficult.

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  • $\begingroup$ Funny enough while most car manufacturers do also make the engines and drivetrains, they still outsource much of the electronic controllers, and the departments in large companies behave almost as independent companies anyway. I'd rather lean towards saying that the automotive situation is simpler because everybody at least can do CAN and because the buses used are not as crazy resilient as the ARINC429 where every transmitter transmits in a separate line so they never need to tap as many wires. $\endgroup$ – Jan Hudec Mar 17 at 22:27

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