I am trying to trigger the flash codes but from what i could find online doesn't help me locate what i am looking for. Does anyone have any suggestions on where this OBD 1 is. i checked driverside where it is suppose to be but can not locate a Trapezoid shape plug.

 

you will not get any because the 89 7.3 diesel is full mechanical. the only time the check engine light will come on is if no oil pressure, or high coolant temperature.

 

okay that makes sense. Thank you!