General [Resolved] OBD1 Diagnostic Port bypass/wiring from ECU questions

[Salad 419]

The REAL version of the story is that I bought a Colt with a 4G63T swap in progress and need to finish some wiring issues, but thought it may be easier to just "hotwire" than to find all of the missing wires since the wiring was a hack job.

My basic question is, can you "hotwire" the ECU to make your own "diagnostic port" so I can log?

I'm pretty sure all I have to do is connect to ECU Pin 2 Diagnosis/Data transfer select terminal (which will be my data wire). BUT, how do you "ground" the ECU to place it in diagnostic mode? Said another way, how should I replicate the grounding of 10 and 12 of the diagnostic port? There are 3 ground wires on the ECU, Pins 101,104,106 but I'm not sure they have anything to do with this or if I just ground another wire to place the ECU into diagnostic mode.

Anybody that knows how this ECU works so I can duplicate it please help. Thanks for the space.

 

[steve]

Pick your connector, it doesn't have to be a OBD I style.
You need three pins, Data (ECU pin 1), Mode (ECU pin 2), and Ground.

Steve

 

[Salad 419]

Okay, so is this my new "wiring diagram" and do I have the basics down?

ECU Pin 1 is where the information is sent?
ECU Pin 2 gets grounded to set the computer into diagnostic mode?

If this is the case, then I'd just tap into ECU Pin 1 for my data wire from my pocket logger, and ground the ECU Pin 2 and connect the "ground" wire from my pocket logger to that as well and it's that simple? Or did I completely mess it up?

Thanks

 

[steve]

Almost, you have to remember that the signals coming and going to pin 1 need a return path for the current and the ground is used for that. The datalogger circuit uses the ground to complete the data circuit and to pull the mode line low to switch the ECU into datalogging mode.

Steve