OBD-II (On Board Diagnostics II) is a description of the engine control system. The first computer controlled cars had what was loosely termed "OBD-I" or the first generation of on-baord diagnostics. In this system, a sensor failure might only be caught once the sensor had completely died. For example, a TPS code might get set only if the sensor reads below 0.1V or over 4.9V.dig_dug_mx6 said:I saw this in a post in the lounge section and i was wondering what this is and what problems there are putting on performance parts???
That's my understanding. The NVM (non-volatile memory) in the OBD-I PCM is simply a battery-backed RAM in the processor itself, kept alive by an always-hot battery feed. When the battery is disconnected, the RAM loses the stored codes. Usually, the PCM will do a checksum or other integrity check of that memory each boot-up and if the integrity is in error, it will clear and reset that memory itself. This is what a battery reset usually does.Greg S said:Mike,
Doesn't OBD-II permantly record any error codes sot hat htey can be pulled up when you have an emissions test?