by MalibuJack » Wed May 16, 2007 6:53 am
On the Evo, it basically acts as a switch to ground, so you provide 12v to the indicator light, then instead of the ground, you run it to the ECU's CEL indicator pin, which basically closes to ground.
On the Evo, the Ignition switch is a 12v+ source which tells it the key is on, and the pin on the ECU expects to see 12v+ on its Key-On pin to indicate the ECU should wake up.
On the Evo, there are 3 pins used for power, two are main power, one is battery backup. They all should get power.
Basically in order to simulate the function of the car's running state, I switched the ignition keyon voltage source, the voltage source to the main ECU power, and a voltage source to the backup power. This in turn allows me to simulate battery disconnect, accessory power only, and engine running state. (its necessary to test the persistence of some settings in ram that we're developing on aktivematrix)
In the two threads dedicated to my bench harness, both have photos of the unit I built, and one had details on all the pinouts for the Evo, however I have not attempted to build a Subaru bench harness as I don't currently have the need for it. I have a more pressing need for a evo IX bench harness as it uses a newer ECU design which has different connections, but I haven't wanted to cut up a perfectly good $150 ECU Extension harness for it, so I'm waiting for Summimoto or AMP to make some stock available.