Many old cars are still in circulation, and those that are equipped with an injection system with only 1 injector, have a very limited diagnostic range.
The EEC-IV offers OBD-I diagnostics, and the codes are stored inside the EEC via KAM. KAM (Keep-Alive Memory) will ensure the codes are not erased if main power is low, although removing power altogether (disconnecting the battery completely) will completely erase any diagnostic codes stored in the EEC-IV module once the internal capacitors have completely discharged. The KAM is composed of a separate wire running to the battery, and the KAM consumes low power. The KAM EEPROM is 128 bytes large.
The EEC-IV has two modes of self-testing. These self-tests are found in almost any ECU after or during the mid-late 1980s, and are found in almost all (if not all) ECU modules produced today. These diagnostic self-tests are KOEO (Key On, Engine Off) and KOER (Key On, Engine Running). It is normal for your "Check Engine" light to illuminate while the key is in the "ON" position, but the engine is NOT running. (This means the ECU is operating normally.)
The diagnostic codes can be pulled by a dealer or auto-parts store using an OBD-I code reader. The diagnostic port is located under the hood. On the Pintomobile, a 1989 Ford F-150, the OBD-I port was located above the front driver side wheel well. It is a grey connector with it not connected to anything, although it may be hiding under a black plastic cover (this black plastic cover likes to fall off over time. Mine has fallen off.) The EEC-IV module is located in different places in different cars. My 1989 Ford F-150 has the EEC-IV module located "in" the firewall on the driverside. (This area is often referred to as the "driver side kickpanel.")
Later ECUs use OBD-II, which typically has the port inside the cabin. OBD-II is much more advanced in comparison to OBD-I.
Source: 404 - Page Not Found :: Garrett Fuller - Digital Media Professional
I found a simulator project for ODB2, and I was thinking about adapting it in an ODB1 system, to be able to more easily monitor the state of the sensors and actuators.
Ive been building an Arduino OBD2 Scanner to interface with my Jeep's OBD2 port, but it became a beeeeeg! schlep to upload code to my Arduino Nano + 16x2 LCD + ELM327 Scanner device, then haul the whole prototype to the Jeep in the gurage the whole time and then only to find there was something small i forgot to change.
I needed to find a way to test my prototype in the comfort of my home.
Ive searched high and low and couldn't find any Arduino OBD2 simulators that i can build my self. I came across one or two websites that's making use of Arduino to build an OBD2 Simulator but they dont give you the code you have to buy the ready made product from them, I.E the FreeMatics for something like a whopping $169, Wheres the love for Open source in that ???? pffft! I dont see $169 I see about 8 Arduinos i can buy with it.
So unfortunatly and fortunatly for you
I had to figure out how i'm going to build one my self, which forced me to now focus on a project i had to take on in order to complete my initial project, Took me some time to figure out how to send PIDs in standard OBD2 format. But at the end i could connect a FreeObd Scanner program which you normally get with your ELM327 Scanner.
Has anyone seen any such project? It would not be an update of the OBD1 system, but an addition of monitoring with ODB2 protocol to facilitate the use of tools already available.