My cousin recently installed a 91 Si head on his 93 DX. The car runs great w/ the DX ECU, but when we installed the p28 - it ran even better. But the question I was wondering is why the check engine light stays on and how or what would we need to do to turn the light off. I have already done the search on all the 8 pages through archived files and none has answered this question.

Any help would be appreciated.

 

mini me is not using 91 non vtec head on another non vtec head.

what you have is DX motor with another DX head but slightly better cams.

DX ECU is non vtec and so is the setup. the P28 is sohc vtec ecu. check engine/CEL you;re getting is 21 and 22 (basically related to VTEC, solenoid and pressure switch not being there)

p28 is only giving you an illusion of feeling better then DX as the maps you're running with it are low cam and very lean and rev limit of about 7000rpm or so.