I'm having a issue with the check engine light on my 1999 Prelude running a jumper harness to run a obd1 P72 ecu (turbo car, h22a engine, obd1 distributor etc). When I first turn on the car the light comes on and goes off like it should so I thought the light was working. My car is running like hell and figure there could be a sensor issue so I tested the light by unplugging the map sensor and starting the car and the light did not come on (shouldn't an unplugged map sensor trigger the cel?)

I also noticed when I jump the blue plug to check to see if there are any saved codes I get a constant engine light on the dash which only goes out when I unplug the jumper (no flashes etc).

Any advice as to what I should look for would be appreciated.

 

what "chip" are you running? Unplug the jumper to use the internal rom and see if you get any codes that way.

 

Hondata has been written on the ecu casing, but since I wasn't the one who had the car tuned I am not sure. I will do what you said and let you know tomorrow what comes up. Thank you for the help!